diff --git a/src/bin_client/test/test_contracts.sh b/src/bin_client/test/test_contracts.sh
index ef87464bf..7bd36e8c8 100755
--- a/src/bin_client/test/test_contracts.sh
+++ b/src/bin_client/test/test_contracts.sh
@@ -208,7 +208,7 @@ assert_output $contract_dir/exec_concat.tz Unit '""' '"_abc"'
 assert_output $contract_dir/exec_concat.tz Unit '"test"' '"test_abc"'
 
 # Get current steps to quota
-assert_output $contract_dir/steps_to_quota.tz Unit Unit 39968
+assert_output $contract_dir/steps_to_quota.tz Unit Unit 39989
 
 # Get the current balance of the contract
 assert_output $contract_dir/balance.tz Unit Unit '"4,000,000"'
diff --git a/src/proto_alpha/lib_client/client_proto_args.ml b/src/proto_alpha/lib_client/client_proto_args.ml
index e0fdbddc1..a36daa55b 100644
--- a/src/proto_alpha/lib_client/client_proto_args.ml
+++ b/src/proto_alpha/lib_client/client_proto_args.ml
@@ -149,6 +149,20 @@ let fee_arg =
     ~parameter:"fee"
     ~doc:"fee in \xEA\x9C\xA9 to pay to the baker"
 
+let gas_limit_arg =
+  arg
+    ~long:"gas-limit"
+    ~short:'G'
+    ~placeholder:"amount"
+    ~doc:"Set the gas limit of the transaction instead \
+          of letting the client decide based on a simulation"
+    (parameter (fun _ s ->
+         try
+           let v = Z.of_string s in
+           assert Compare.Z.(v >= Z.zero) ;
+           return v
+         with _ -> failwith "invalid gas limit (must be a positive number)"))
+
 let max_priority_arg =
   arg
     ~long:"max-priority"
diff --git a/src/proto_alpha/lib_client/client_proto_args.mli b/src/proto_alpha/lib_client/client_proto_args.mli
index d0e26374a..08fc898c7 100644
--- a/src/proto_alpha/lib_client/client_proto_args.mli
+++ b/src/proto_alpha/lib_client/client_proto_args.mli
@@ -14,6 +14,7 @@ val tez_sym: string
 
 val init_arg: (string, Proto_alpha.full) Clic.arg
 val fee_arg: (Tez.t, Proto_alpha.full) Clic.arg
+val gas_limit_arg: (Z.t option, Proto_alpha.full) Clic.arg
 val arg_arg: (string, Proto_alpha.full) Clic.arg
 val source_arg: (string option, Proto_alpha.full) Clic.arg
 
diff --git a/src/proto_alpha/lib_client/client_proto_context.ml b/src/proto_alpha/lib_client/client_proto_context.ml
index eb2305a85..04f1c63f2 100644
--- a/src/proto_alpha/lib_client/client_proto_context.ml
+++ b/src/proto_alpha/lib_client/client_proto_context.ml
@@ -36,9 +36,9 @@ let parse_expression arg =
     (Micheline_parser.no_parsing_error
        (Michelson_v1_parser.parse_expression arg))
 
-let transfer cctxt
+let transfer (cctxt : #Proto_alpha.full)
     block ?branch
-    ~source ~src_pk ~src_sk ~destination ?arg ~amount ~fee () =
+    ~source ~src_pk ~src_sk ~destination ?arg ~amount ~fee ?gas_limit () =
   get_branch cctxt block branch >>=? fun (chain_id, branch) ->
   begin match arg with
     | Some arg ->
@@ -49,17 +49,43 @@ let transfer cctxt
   Alpha_services.Contract.counter
     cctxt block source >>=? fun pcounter ->
   let counter = Int32.succ pcounter in
+  Block_services.predecessor cctxt block >>=? fun predecessor ->
+  begin match gas_limit with
+    | Some gas_limit -> return gas_limit
+    | None ->
+        Alpha_services.Constants.hard_gas_limits cctxt block >>=? fun (_, max_gas) ->
+        Alpha_services.Forge.Manager.transaction
+          cctxt block
+          ~branch ~source ~sourcePubKey:src_pk ~counter ~amount
+          ~destination ?parameters ~fee ~gas_limit:max_gas () >>=? fun bytes ->
+        Client_keys.sign
+          src_sk ~watermark:Generic_operation bytes >>=? fun signature ->
+        let signed_bytes = Signature.concat bytes signature in
+        let oph = Operation_hash.hash_bytes [ signed_bytes ] in
+        Alpha_services.Helpers.apply_operation cctxt block
+          predecessor oph bytes (Some signature) >>=? fun (_, gas) ->
+        match gas with
+        | Limited { remaining } ->
+            let gas = Z.sub max_gas remaining in
+            if Z.equal gas Z.zero then
+              cctxt#message "Estimated gas: none" >>= fun () ->
+              return Z.zero
+            else
+              let gas = Z.sub max_gas remaining in
+              cctxt#message "Estimated gas: %s units (will add 100 for safety)" (Z.to_string gas) >>= fun () ->
+              return (Z.add gas (Z.of_int 100))
+        | Unaccounted -> assert false
+  end >>=? fun gas_limit ->
   Alpha_services.Forge.Manager.transaction
     cctxt block
     ~branch ~source ~sourcePubKey:src_pk ~counter ~amount
-    ~destination ?parameters ~fee () >>=? fun bytes ->
-  Block_services.predecessor cctxt block >>=? fun predecessor ->
+    ~destination ?parameters ~fee ~gas_limit () >>=? fun bytes ->
   Client_keys.sign
     src_sk ~watermark:Generic_operation bytes >>=? fun signature ->
   let signed_bytes = Signature.concat bytes signature in
   let oph = Operation_hash.hash_bytes [ signed_bytes ] in
   Alpha_services.Helpers.apply_operation cctxt block
-    predecessor oph bytes (Some signature) >>=? fun contracts ->
+    predecessor oph bytes (Some signature) >>=? fun (contracts, _gas) ->
   Shell_services.inject_operation
     cctxt ~chain_id signed_bytes >>=? fun injected_oph ->
   assert (Operation_hash.equal oph injected_oph) ;
@@ -91,12 +117,12 @@ let originate rpc_config ?chain_id ~block ?signature bytes =
   let oph = Operation_hash.hash_bytes [ signed_bytes ] in
   Alpha_services.Helpers.apply_operation rpc_config block
     predecessor oph bytes signature >>=? function
-  | [ contract ] ->
+  | [ contract ], _ ->
       Shell_services.inject_operation
         rpc_config ?chain_id signed_bytes >>=? fun injected_oph ->
       assert (Operation_hash.equal oph injected_oph) ;
       return (oph, contract)
-  | contracts ->
+  | contracts, _ ->
       failwith
         "The origination introduced %d contracts instead of one."
         (List.length contracts)
@@ -121,7 +147,7 @@ let originate_account ?branch
   Alpha_services.Forge.Manager.origination cctxt block
     ~branch ~source ~sourcePubKey:src_pk ~managerPubKey:manager_pkh
     ~counter ~balance ~spendable:true
-    ?delegatable ?delegatePubKey:delegate ~fee () >>=? fun bytes ->
+    ?delegatable ?delegatePubKey:delegate ~fee ~gas_limit:Z.zero () >>=? fun bytes ->
   Client_keys.sign
     src_sk ~watermark:Generic_operation bytes >>=? fun signature ->
   originate cctxt ~block ~chain_id ~signature bytes
@@ -216,6 +242,7 @@ let save_contract ~force cctxt alias_name contract =
 
 let originate_contract
     ~fee
+    ?gas_limit
     ~delegate
     ?(delegatable=true)
     ?(spendable=false)
@@ -235,11 +262,38 @@ let originate_contract
     cctxt block source >>=? fun pcounter ->
   let counter = Int32.succ pcounter in
   get_branch cctxt block None >>=? fun (_chain_id, branch) ->
+  begin match gas_limit with
+    | Some gas_limit -> return gas_limit
+    | None ->
+        Alpha_services.Constants.hard_gas_limits cctxt block >>=? fun (_, max_gas) ->
+        Alpha_services.Forge.Manager.origination cctxt block
+          ~branch ~source ~sourcePubKey:src_pk ~managerPubKey:manager
+          ~counter ~balance ~spendable:spendable
+          ~delegatable ?delegatePubKey:delegate
+          ~script:{ code ; storage } ~fee  ~gas_limit:max_gas () >>=? fun bytes ->
+        Client_keys.sign
+          ~watermark:Generic_operation src_sk bytes >>=? fun signature ->
+        let signed_bytes = Signature.concat bytes signature in
+        let oph = Operation_hash.hash_bytes [ signed_bytes ] in
+        Block_services.predecessor cctxt block >>=? fun predecessor ->
+        Alpha_services.Helpers.apply_operation cctxt block
+          predecessor oph bytes (Some signature) >>=? fun (_, gas) ->
+        match gas with
+        | Limited { remaining } ->
+            let gas = Z.sub max_gas remaining in
+            if Z.equal gas Z.zero then
+              cctxt#message "Estimated gas: none" >>= fun () ->
+              return Z.zero
+            else
+              cctxt#message "Estimated gas: %s units (will add 100 for safety)" (Z.to_string gas) >>= fun () ->
+              return (Z.add gas (Z.of_int 100))
+        | Unaccounted -> assert false
+  end >>=? fun gas_limit ->
   Alpha_services.Forge.Manager.origination cctxt block
     ~branch ~source ~sourcePubKey:src_pk ~managerPubKey:manager
     ~counter ~balance ~spendable:spendable
     ~delegatable ?delegatePubKey:delegate
-    ~script:{ code ; storage } ~fee () >>=? fun bytes ->
+    ~script:{ code ; storage } ~fee ~gas_limit () >>=? fun bytes ->
   Client_keys.sign
     src_sk ~watermark:Generic_operation bytes >>=? fun signature ->
   originate cctxt ~block ~signature bytes
diff --git a/src/proto_alpha/lib_client/client_proto_context.mli b/src/proto_alpha/lib_client/client_proto_context.mli
index d2954c151..334dbd3f1 100644
--- a/src/proto_alpha/lib_client/client_proto_context.mli
+++ b/src/proto_alpha/lib_client/client_proto_context.mli
@@ -91,6 +91,7 @@ val operation_submitted_message :
 
 val originate_contract:
   fee:Tez.t ->
+  ?gas_limit:Z.t ->
   delegate:public_key_hash option ->
   ?delegatable:bool ->
   ?spendable:bool ->
@@ -115,6 +116,7 @@ val transfer :
   ?arg:string ->
   amount:Tez.t ->
   fee:Tez.t ->
+  ?gas_limit:Z.t ->
   unit ->
   (Operation_hash.t * Contract.t list) tzresult Lwt.t
 
diff --git a/src/proto_alpha/lib_client/client_proto_programs.mli b/src/proto_alpha/lib_client/client_proto_programs.mli
index 1afa7e93d..619499747 100644
--- a/src/proto_alpha/lib_client/client_proto_programs.mli
+++ b/src/proto_alpha/lib_client/client_proto_programs.mli
@@ -51,7 +51,7 @@ val print_trace_result :
     tzresult -> unit tzresult Lwt.t
 
 val hash_and_sign :
-  ?gas:int ->
+  ?gas:Z.t ->
   Michelson_v1_parser.parsed ->
   Michelson_v1_parser.parsed ->
   Client_keys.sk_uri ->
@@ -60,7 +60,7 @@ val hash_and_sign :
   (string * string * Gas.t) tzresult Lwt.t
 
 val typecheck_data :
-  ?gas:int ->
+  ?gas:Z.t ->
   data:Michelson_v1_parser.parsed ->
   ty:Michelson_v1_parser.parsed ->
   'a ->
@@ -68,7 +68,7 @@ val typecheck_data :
   Gas.t tzresult Lwt.t
 
 val typecheck_program :
-  ?gas:int ->
+  ?gas:Z.t ->
   Michelson_v1_parser.parsed ->
   Block_services.block ->
   #Proto_alpha.rpc_context ->
diff --git a/src/proto_alpha/lib_client/michelson_v1_error_reporter.ml b/src/proto_alpha/lib_client/michelson_v1_error_reporter.ml
index 08812bc25..675e6eb6e 100644
--- a/src/proto_alpha/lib_client/michelson_v1_error_reporter.ml
+++ b/src/proto_alpha/lib_client/michelson_v1_error_reporter.ml
@@ -206,9 +206,14 @@ let report_errors ~details ~show_source ?parsed ppf errs =
           print_source (parsed, hilights) ;
         if rest <> [] then Format.fprintf ppf "@," ;
         print_trace (parsed_locations parsed) rest
-    | Alpha_environment.Ecoproto_error Gas.Quota_exceeded :: rest ->
+    | Alpha_environment.Ecoproto_error Gas.Block_quota_exceeded :: rest ->
         Format.fprintf ppf
-          "@[<v 0>Gas limit exceeded during typechecking or execution. Try again with a higher gas limit.@]" ;
+          "@[<v 0>Gas limit for the block exceeded during typechecking or execution.@]" ;
+        if rest <> [] then Format.fprintf ppf "@," ;
+        print_trace locations rest
+    | Alpha_environment.Ecoproto_error Gas.Operation_quota_exceeded :: rest ->
+        Format.fprintf ppf
+          "@[<v 0>Gas limit exceeded during typechecking or execution.@,Try again with a higher gas limit.@]" ;
         if rest <> [] then Format.fprintf ppf "@," ;
         print_trace locations rest
     | Alpha_environment.Ecoproto_error err :: rest ->
diff --git a/src/proto_alpha/lib_client_commands/client_proto_context_commands.ml b/src/proto_alpha/lib_client_commands/client_proto_context_commands.ml
index c93ae28df..486c8ca5f 100644
--- a/src/proto_alpha/lib_client_commands/client_proto_context_commands.ml
+++ b/src/proto_alpha/lib_client_commands/client_proto_context_commands.ml
@@ -181,8 +181,8 @@ let commands () =
       end ;
 
     command ~group ~desc: "Launch a smart contract on the blockchain."
-      (args7
-         fee_arg delegate_arg (Client_keys.force_switch ())
+      (args8
+         fee_arg gas_limit_arg delegate_arg (Client_keys.force_switch ())
          delegatable_switch spendable_switch init_arg no_print_source_flag)
       (prefixes [ "originate" ; "contract" ]
        @@ RawContractAlias.fresh_alias_param
@@ -201,12 +201,12 @@ let commands () =
          ~name:"prg" ~desc: "script of the account\n\
                              Combine with -init if the storage type is not unit."
        @@ stop)
-      begin fun (fee, delegate, force, delegatable, spendable, initial_storage, no_print_source)
+      begin fun (fee, gas_limit, delegate, force, delegatable, spendable, initial_storage, no_print_source)
         alias_name manager balance (_, source) program (cctxt : Proto_alpha.full) ->
         RawContractAlias.of_fresh cctxt force alias_name >>=? fun alias_name ->
         Lwt.return (Micheline_parser.no_parsing_error program) >>=? fun { expanded = code } ->
         source_to_keys cctxt cctxt#block source >>=? fun (src_pk, src_sk) ->
-        originate_contract ~fee ~delegate ~delegatable ~spendable ~initial_storage
+        originate_contract ~fee ?gas_limit ~delegate ~delegatable ~spendable ~initial_storage
           ~manager ~balance ~source ~src_pk ~src_sk ~code cctxt >>= fun errors ->
         report_michelson_errors ~no_print_source ~msg:"origination simulation failed" cctxt errors >>= function
         | None -> return ()
@@ -217,7 +217,7 @@ let commands () =
       end ;
 
     command ~group ~desc: "Transfer tokens / call a smart contract."
-      (args3 fee_arg arg_arg no_print_source_flag)
+      (args4 fee_arg gas_limit_arg arg_arg no_print_source_flag)
       (prefixes [ "transfer" ]
        @@ tez_param
          ~name: "qty" ~desc: "amount taken from source"
@@ -228,10 +228,10 @@ let commands () =
        @@ ContractAlias.destination_param
          ~name: "dst" ~desc: "name/literal of the destination contract"
        @@ stop)
-      begin fun (fee, arg, no_print_source) amount (_, source) (_, destination) cctxt ->
+      begin fun (fee, gas_limit, arg, no_print_source) amount (_, source) (_, destination) cctxt ->
         source_to_keys cctxt cctxt#block source >>=? fun (src_pk, src_sk) ->
         transfer cctxt ~fee cctxt#block
-          ~source ~src_pk ~src_sk ~destination ~arg ~amount () >>=
+          ~source ~src_pk ~src_sk ~destination ~arg ~amount ?gas_limit () >>=
         report_michelson_errors ~no_print_source ~msg:"transfer simulation failed" cctxt >>= function
         | None -> return ()
         | Some (oph, contracts) ->
diff --git a/src/proto_alpha/lib_client_commands/client_proto_programs_commands.ml b/src/proto_alpha/lib_client_commands/client_proto_programs_commands.ml
index 5c6a1bb43..eccf0e502 100644
--- a/src/proto_alpha/lib_client_commands/client_proto_programs_commands.ml
+++ b/src/proto_alpha/lib_client_commands/client_proto_programs_commands.ml
@@ -47,14 +47,15 @@ let commands () =
       ~short:'G'
       ~doc:"Initial quantity of gas for typechecking and execution"
       ~placeholder:"gas"
-      (parameter
-         (fun _ctx str ->
-            try
-              return (int_of_string str)
-            with _ ->
-              failwith "Invalid gas literal: '%s'" str)) in
-  let resolve_max_gas ctxt block = function
-    | None -> Alpha_services.Constants.max_gas ctxt block >>=? fun gas ->
+      (parameter (fun _ctx str ->
+           try
+             let v = Z.of_string str in
+             assert Compare.Z.(v >= Z.zero) ;
+             return v
+           with _ -> failwith "invalid gas limit (must be a positive number)")) in
+  let resolve_max_gas cctxt block = function
+    | None ->
+        Alpha_services.Constants.hard_gas_limits cctxt block >>=? fun (_, gas) ->
         return gas
     | Some gas -> return gas in
   let data_parameter =
diff --git a/src/proto_alpha/lib_protocol/src/alpha_context.ml b/src/proto_alpha/lib_protocol/src/alpha_context.ml
index 010805b41..b8dfbbbfa 100644
--- a/src/proto_alpha/lib_protocol/src/alpha_context.ml
+++ b/src/proto_alpha/lib_protocol/src/alpha_context.ml
@@ -67,6 +67,7 @@ module Gas = struct
   let set_unlimited = Raw_context.set_gas_unlimited
   let consume = Raw_context.consume_gas
   let level = Raw_context.gas_level
+  let block_level = Raw_context.block_gas_level
 end
 module Level = struct
   include Level_repr
diff --git a/src/proto_alpha/lib_protocol/src/alpha_context.mli b/src/proto_alpha/lib_protocol/src/alpha_context.mli
index 2aa0c0eaa..258c91712 100644
--- a/src/proto_alpha/lib_protocol/src/alpha_context.mli
+++ b/src/proto_alpha/lib_protocol/src/alpha_context.mli
@@ -109,7 +109,7 @@ end
 module Gas : sig
   type t = private
     | Unaccounted
-    | Limited of { remaining : int }
+    | Limited of { remaining : Z.t }
 
   val encoding : t Data_encoding.encoding
   val pp : Format.formatter -> t -> unit
@@ -119,7 +119,8 @@ module Gas : sig
   val cost_encoding : cost Data_encoding.encoding
   val pp_cost : Format.formatter -> cost -> unit
 
-  type error += Quota_exceeded
+  type error += Block_quota_exceeded (* `Temporary *)
+  type error += Operation_quota_exceeded (* `Temporary *)
 
   val free : cost
   val step_cost : int -> cost
@@ -130,10 +131,11 @@ module Gas : sig
   val ( *@ ) : int -> cost -> cost
   val ( +@ ) : cost -> cost -> cost
 
-  val set_limit: context -> int -> context
+  val set_limit: context -> Z.t -> context tzresult
   val set_unlimited: context -> context
   val consume: context -> cost -> context tzresult
   val level: context -> t
+  val block_level: context -> Z.t
 end
 
 module Script_int : module type of Script_int_repr
@@ -299,7 +301,8 @@ module Constants : sig
     time_between_blocks: Period.t list ;
     first_free_baking_slot: int ;
     endorsers_per_block: int ;
-    max_gas: int ;
+    hard_gas_limit_per_operation: Z.t ;
+    hard_gas_limit_per_block: Z.t ;
     proof_of_work_threshold: int64 ;
     dictator_pubkey: Signature.Public_key.t ;
     max_operation_data_length: int ;
@@ -323,7 +326,8 @@ module Constants : sig
   val time_between_blocks: context -> Period.t list
   val first_free_baking_slot: context -> int
   val endorsers_per_block: context -> int
-  val max_gas: context -> int
+  val hard_gas_limit_per_operation: context -> Z.t
+  val hard_gas_limit_per_block: context -> Z.t
   val proof_of_work_threshold: context -> int64
   val dictator_pubkey: context -> Signature.Public_key.t
   val max_operation_data_length: context -> int
@@ -764,6 +768,7 @@ and manager_operation =
       amount: Tez.t ;
       parameters: Script.expr option ;
       destination: Contract.contract ;
+      gas_limit: Z.t;
     }
   | Origination of {
       manager: public_key_hash ;
@@ -772,6 +777,7 @@ and manager_operation =
       spendable: bool ;
       delegatable: bool ;
       credit: Tez.t ;
+      gas_limit: Z.t;
     }
   | Delegation of public_key_hash option
 
diff --git a/src/proto_alpha/lib_protocol/src/apply.ml b/src/proto_alpha/lib_protocol/src/apply.ml
index a59fe3538..7ccfb5377 100644
--- a/src/proto_alpha/lib_protocol/src/apply.ml
+++ b/src/proto_alpha/lib_protocol/src/apply.ml
@@ -371,8 +371,8 @@ let apply_amendment_operation_content ctxt delegate = function
 let apply_manager_operation_content
     ctxt origination_nonce source = function
   | Reveal _ -> return (ctxt, origination_nonce, None)
-  | Transaction { amount ; parameters ; destination } ->
-      let ctxt = Gas.set_limit ctxt (Constants.max_gas ctxt) in
+  | Transaction { amount ; parameters ; destination ; gas_limit } ->
+      Lwt.return (Gas.set_limit ctxt gas_limit) >>=? fun ctxt ->
       begin
         Contract.spend ctxt source amount >>=? fun ctxt ->
         Contract.credit ctxt destination amount >>=? fun ctxt ->
@@ -422,8 +422,8 @@ let apply_manager_operation_content
             | None, _ -> fail (Bad_contract_parameter (destination, Some arg_type, None))
       end
   | Origination { manager ; delegate ; script ;
-                  spendable ; delegatable ; credit } ->
-      let ctxt = Gas.set_limit ctxt (Constants.max_gas ctxt) in
+                  spendable ; delegatable ; credit ; gas_limit } ->
+      Lwt.return (Gas.set_limit ctxt gas_limit) >>=? fun ctxt ->
       begin match script with
         | None -> return (None, None, ctxt)
         | Some script ->
@@ -488,7 +488,6 @@ let apply_sourced_operation
                 ctxt origination_nonce source content)
         (ctxt, origination_nonce, None) contents
       >>=? fun (ctxt, origination_nonce, err) ->
-      let ctxt = Gas.set_unlimited ctxt in
       return (ctxt, origination_nonce, err)
   | Consensus_operation content ->
       apply_consensus_operation_content ctxt
@@ -616,22 +615,25 @@ let apply_anonymous_operation ctxt _delegate origination_nonce kind =
 
 let apply_operation
     ctxt delegate pred_block block_prio hash operation =
+  begin match operation.contents with
+    | Anonymous_operations ops ->
+        let origination_nonce = Contract.initial_origination_nonce hash in
+        fold_left_s
+          (fun (ctxt, origination_nonce) op ->
+             apply_anonymous_operation ctxt delegate origination_nonce op)
+          (ctxt, origination_nonce) ops
+        >>=? fun (ctxt, origination_nonce) ->
+        return (ctxt, Contract.originated_contracts origination_nonce, None)
+    | Sourced_operations op ->
+        let origination_nonce = Contract.initial_origination_nonce hash in
+        apply_sourced_operation
+          ctxt pred_block block_prio
+          operation origination_nonce op >>=? fun (ctxt, origination_nonce, err) ->
+        return (ctxt, Contract.originated_contracts origination_nonce, err)
+  end >>=? fun (ctxt, contracts, err) ->
+  let gas = Gas.level ctxt in
   let ctxt = Gas.set_unlimited ctxt in
-  match operation.contents with
-  | Anonymous_operations ops ->
-      let origination_nonce = Contract.initial_origination_nonce hash in
-      fold_left_s
-        (fun (ctxt, origination_nonce) op ->
-           apply_anonymous_operation ctxt delegate origination_nonce op)
-        (ctxt, origination_nonce) ops
-      >>=? fun (ctxt, origination_nonce) ->
-      return (ctxt, Contract.originated_contracts origination_nonce, None)
-  | Sourced_operations op ->
-      let origination_nonce = Contract.initial_origination_nonce hash in
-      apply_sourced_operation
-        ctxt pred_block block_prio
-        operation origination_nonce op >>=? fun (ctxt, origination_nonce, err) ->
-      return (ctxt, Contract.originated_contracts origination_nonce, err)
+  return (ctxt, gas, contracts, err)
 
 let may_snapshot_roll ctxt =
   let level = Alpha_context.Level.current ctxt in
diff --git a/src/proto_alpha/lib_protocol/src/constants_repr.ml b/src/proto_alpha/lib_protocol/src/constants_repr.ml
index d45683640..c1ba203a0 100644
--- a/src/proto_alpha/lib_protocol/src/constants_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/constants_repr.ml
@@ -52,7 +52,8 @@ type parametric = {
   time_between_blocks: Period_repr.t list ;
   first_free_baking_slot: int ;
   endorsers_per_block: int ;
-  max_gas: int ;
+  hard_gas_limit_per_operation: Z.t ;
+  hard_gas_limit_per_block: Z.t ;
   proof_of_work_threshold: int64 ;
   dictator_pubkey: Signature.Public_key.t ;
   max_operation_data_length: int ;
@@ -76,7 +77,8 @@ let default = {
     List.map Period_repr.of_seconds_exn [ 60L ] ;
   first_free_baking_slot = 16 ;
   endorsers_per_block = 32 ;
-  max_gas = 40_000 ;
+  hard_gas_limit_per_operation = Z.of_int 40_000 ;
+  hard_gas_limit_per_block = Z.of_int 4_000_000 ;
   proof_of_work_threshold =
     Int64.(sub (shift_left 1L 56) 1L) ;
   dictator_pubkey =
@@ -113,9 +115,10 @@ let parametric_encoding =
           c.time_between_blocks,
           c.first_free_baking_slot,
           c.endorsers_per_block,
-          c.max_gas,
-          c.proof_of_work_threshold ),
-        ( c.dictator_pubkey,
+          c.hard_gas_limit_per_operation,
+          c.hard_gas_limit_per_block),
+        ((c.proof_of_work_threshold,
+          c.dictator_pubkey,
           c.max_operation_data_length,
           c.tokens_per_roll,
           c.michelson_maximum_type_size,
@@ -123,8 +126,8 @@ let parametric_encoding =
           c.origination_burn,
           c.block_security_deposit,
           c.endorsement_security_deposit,
-          c.block_reward,
-          c.endorsement_reward)) )
+          c.block_reward),
+         (c.endorsement_reward))) )
     (fun (( preserved_cycles,
             blocks_per_cycle,
             blocks_per_commitment,
@@ -133,9 +136,10 @@ let parametric_encoding =
             time_between_blocks,
             first_free_baking_slot,
             endorsers_per_block,
-            max_gas,
-            proof_of_work_threshold ),
-          ( dictator_pubkey,
+            hard_gas_limit_per_operation,
+            hard_gas_limit_per_block),
+          ((proof_of_work_threshold,
+            dictator_pubkey,
             max_operation_data_length,
             tokens_per_roll,
             michelson_maximum_type_size,
@@ -143,8 +147,8 @@ let parametric_encoding =
             origination_burn,
             block_security_deposit,
             endorsement_security_deposit,
-            block_reward,
-            endorsement_reward )) ->
+            block_reward),
+           (endorsement_reward))) ->
       { preserved_cycles ;
         blocks_per_cycle ;
         blocks_per_commitment ;
@@ -153,7 +157,8 @@ let parametric_encoding =
         time_between_blocks ;
         first_free_baking_slot ;
         endorsers_per_block ;
-        max_gas ;
+        hard_gas_limit_per_operation ;
+        hard_gas_limit_per_block ;
         proof_of_work_threshold ;
         dictator_pubkey ;
         max_operation_data_length ;
@@ -176,19 +181,22 @@ let parametric_encoding =
           (req "time_between_blocks" (list Period_repr.encoding))
           (req "first_free_baking_slot" uint16)
           (req "endorsers_per_block" uint16)
-          (req "instructions_per_transaction" int31)
-          (req "proof_of_work_threshold" int64))
-       (obj10
-          (req "dictator_pubkey" Signature.Public_key.encoding)
-          (req "max_operation_data_length" int31)
-          (req "tokens_per_roll" Tez_repr.encoding)
-          (req "michelson_maximum_type_size" uint16)
-          (req "seed_nonce_revelation_tip" Tez_repr.encoding)
-          (req "origination_burn" Tez_repr.encoding)
-          (req "block_security_deposit" Tez_repr.encoding)
-          (req "endorsement_security_deposit" Tez_repr.encoding)
-          (req "block_reward" Tez_repr.encoding)
-          (req "endorsement_reward" Tez_repr.encoding)))
+          (req "hard_gas_limit_per_operation" z)
+          (req "hard_gas_limit_per_block" z))
+       (merge_objs
+          (obj10
+             (req "proof_of_work_threshold" int64)
+             (req "dictator_pubkey" Signature.Public_key.encoding)
+             (req "max_operation_data_length" int31)
+             (req "tokens_per_roll" Tez_repr.encoding)
+             (req "michelson_maximum_type_size" uint16)
+             (req "seed_nonce_revelation_tip" Tez_repr.encoding)
+             (req "origination_burn" Tez_repr.encoding)
+             (req "block_security_deposit" Tez_repr.encoding)
+             (req "endorsement_security_deposit" Tez_repr.encoding)
+             (req "block_reward" Tez_repr.encoding))
+          (obj1
+             (req "endorsement_reward" Tez_repr.encoding))))
 
 type t = {
   fixed : fixed ;
diff --git a/src/proto_alpha/lib_protocol/src/constants_services.ml b/src/proto_alpha/lib_protocol/src/constants_services.ml
index 7e0d062e4..ac65b9541 100644
--- a/src/proto_alpha/lib_protocol/src/constants_services.ml
+++ b/src/proto_alpha/lib_protocol/src/constants_services.ml
@@ -80,13 +80,14 @@ module S = struct
       ~output: (obj1 (req "endorsers_per_block" uint16))
       RPC_path.(custom_root / "endorsers_per_block")
 
-  let max_gas =
+  let hard_gas_limits =
     RPC_service.post_service
-      ~description: "Instructions per transaction"
+      ~description: "Hard maximum amount of gas per operation and per block"
       ~query: RPC_query.empty
       ~input: empty
-      ~output: (obj1 (req "instructions_per_transaction" int31))
-      RPC_path.(custom_root / "max_gas")
+      ~output: (obj2 (req "per_block" z) (req "per_operation" z))
+      RPC_path.(custom_root / "hard_gas_limits")
+
 
   let proof_of_work_threshold =
     RPC_service.post_service
@@ -189,8 +190,9 @@ let () =
   register0 S.endorsers_per_block begin fun ctxt () () ->
     return (Constants.endorsers_per_block ctxt)
   end ;
-  register0 S.max_gas begin fun ctxt () () ->
-    return (Constants.max_gas ctxt)
+  register0 S.hard_gas_limits begin fun ctxt () () ->
+    return (Constants.hard_gas_limit_per_block ctxt,
+            Constants.hard_gas_limit_per_operation ctxt)
   end ;
   register0 S.proof_of_work_threshold begin fun ctxt () () ->
     return (Constants.proof_of_work_threshold ctxt)
@@ -238,8 +240,8 @@ let first_free_baking_slot ctxt block =
   RPC_context.make_call0 S.first_free_baking_slot ctxt block () ()
 let endorsers_per_block ctxt block =
   RPC_context.make_call0 S.endorsers_per_block ctxt block () ()
-let max_gas ctxt block =
-  RPC_context.make_call0 S.max_gas ctxt block () ()
+let hard_gas_limits ctxt block =
+  RPC_context.make_call0 S.hard_gas_limits ctxt block () ()
 let proof_of_work_threshold ctxt block =
   RPC_context.make_call0 S.proof_of_work_threshold ctxt block () ()
 let seed_nonce_revelation_tip ctxt block =
diff --git a/src/proto_alpha/lib_protocol/src/constants_services.mli b/src/proto_alpha/lib_protocol/src/constants_services.mli
index 1bb650d5b..d126e4dfe 100644
--- a/src/proto_alpha/lib_protocol/src/constants_services.mli
+++ b/src/proto_alpha/lib_protocol/src/constants_services.mli
@@ -33,8 +33,8 @@ val first_free_baking_slot:
 val endorsers_per_block:
   'a #RPC_context.simple -> 'a -> int shell_tzresult Lwt.t
 
-val max_gas:
-  'a #RPC_context.simple -> 'a -> int shell_tzresult Lwt.t
+val hard_gas_limits:
+  'a #RPC_context.simple -> 'a -> (Z.t * Z.t) shell_tzresult Lwt.t
 
 val proof_of_work_threshold:
   'a #RPC_context.simple -> 'a -> Int64.t shell_tzresult Lwt.t
diff --git a/src/proto_alpha/lib_protocol/src/constants_storage.ml b/src/proto_alpha/lib_protocol/src/constants_storage.ml
index 38154178a..fbd247558 100644
--- a/src/proto_alpha/lib_protocol/src/constants_storage.ml
+++ b/src/proto_alpha/lib_protocol/src/constants_storage.ml
@@ -31,9 +31,12 @@ let first_free_baking_slot c =
 let endorsers_per_block c =
   let constants = Raw_context.constants c in
   constants.endorsers_per_block
-let max_gas c =
+let hard_gas_limit_per_operation c =
   let constants = Raw_context.constants c in
-  constants.max_gas
+  constants.hard_gas_limit_per_operation
+let hard_gas_limit_per_block c =
+  let constants = Raw_context.constants c in
+  constants.hard_gas_limit_per_block
 let proof_of_work_threshold c =
   let constants = Raw_context.constants c in
   constants.proof_of_work_threshold
diff --git a/src/proto_alpha/lib_protocol/src/gas_repr.ml b/src/proto_alpha/lib_protocol/src/gas_repr.ml
index c41268571..468b3f5f7 100644
--- a/src/proto_alpha/lib_protocol/src/gas_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/gas_repr.ml
@@ -9,16 +9,16 @@
 
 type t =
   | Unaccounted
-  | Limited of { remaining : int }
+  | Limited of { remaining : Z.t }
 
 type cost =
-  { allocations : int ;
-    steps : int }
+  { allocations : Z.t ;
+    steps : Z.t }
 
 let encoding =
   let open Data_encoding in
   union
-    [ case (Tag 0) int31
+    [ case (Tag 0) z
         (function Limited { remaining } -> Some remaining | _ -> None)
         (fun remaining -> Limited { remaining }) ;
       case (Tag 1) (constant "unaccounted")
@@ -29,7 +29,7 @@ let pp ppf = function
   | Unaccounted ->
       Format.fprintf ppf "unaccounted"
   | Limited { remaining } ->
-      Format.fprintf ppf "%d units remaining" remaining
+      Format.fprintf ppf "%s units remaining" (Z.to_string remaining)
 
 let cost_encoding =
   let open Data_encoding in
@@ -39,30 +39,40 @@ let cost_encoding =
     (fun (allocations, steps) ->
        { allocations ; steps })
     (obj2
-       (req "allocations" int31)
-       (req "steps" int31))
+       (req "allocations" z)
+       (req "steps" z))
 
 let pp_cost ppf { allocations ; steps } =
   Format.fprintf ppf
-    "(steps: %d, allocs: %d)"
-    steps allocations
+    "(steps: %s, allocs: %s)"
+    (Z.to_string steps) (Z.to_string allocations)
 
-type error += Quota_exceeded
+type error += Block_quota_exceeded (* `Temporary *)
+type error += Operation_quota_exceeded (* `Temporary *)
 
-let consume t cost = match t with
-  | Unaccounted -> ok Unaccounted
+let allocation_weight = Z.of_int 2
+let step_weight = Z.of_int 1
+
+let consume block_gas operation_gas cost = match operation_gas with
+  | Unaccounted -> ok (block_gas, Unaccounted)
   | Limited { remaining } ->
+      let weighted_cost =
+        Z.add
+          (Z.mul allocation_weight cost.allocations)
+          (Z.mul step_weight cost.steps) in
       let remaining =
-        remaining
-        - 2 * cost.allocations
-        - 1 * cost.steps in
-      if Compare.Int.(remaining <= 0)
-      then error Quota_exceeded
-      else ok (Limited { remaining })
+        Z.sub remaining weighted_cost in
+      let block_remaining =
+        Z.sub block_gas weighted_cost in
+      if Compare.Z.(remaining <= Z.zero)
+      then error Operation_quota_exceeded
+      else if Compare.Z.(block_remaining <= Z.zero)
+      then error Block_quota_exceeded
+      else ok (block_remaining, Limited { remaining })
 
 let alloc_cost n =
-  { allocations = n + 1 ;
-    steps = 0 }
+  { allocations = Z.of_int (n + 1) ;
+    steps = Z.zero }
 
 let alloc_bytes_cost n =
   alloc_cost (n / 8)
@@ -71,30 +81,40 @@ let alloc_bits_cost n =
   alloc_cost (n / 64)
 
 let step_cost n =
-  { allocations = 0 ;
-    steps = n }
+  { allocations = Z.zero ;
+    steps = Z.of_int n }
 
 let free =
-  { allocations = 0 ;
-    steps = 0 }
+  { allocations = Z.zero ;
+    steps = Z.zero }
 
 let ( +@ ) x y =
-  { allocations = x.allocations + y.allocations ;
-    steps = x.steps + y.steps }
+  { allocations = Z.add x.allocations y.allocations ;
+    steps = Z.add x.steps y.steps }
 
 let ( *@ ) x y =
-  { allocations = x * y.allocations ;
-    steps = x * y.steps }
+  { allocations = Z.mul (Z.of_int x) y.allocations ;
+    steps = Z.mul (Z.of_int x) y.steps }
 
 let () =
   let open Data_encoding in
   register_error_kind
-    `Permanent
-    ~id:"quotaExceededRuntimeError"
-    ~title: "Quota exceeded (runtime script error)"
+    `Temporary
+    ~id:"gas_exhausted.operation"
+    ~title: "Gas quota exceeded for the operation"
     ~description:
-      "A script or one of its callee took too much \
-       time or storage space"
+      "A script or one of its callee took more \
+       time than the operation said it would"
     empty
-    (function Quota_exceeded -> Some () | _ -> None)
-    (fun () -> Quota_exceeded) ;
+    (function Operation_quota_exceeded -> Some () | _ -> None)
+    (fun () -> Operation_quota_exceeded) ;
+  register_error_kind
+    `Temporary
+    ~id:"gas_exhausted.block"
+    ~title: "Gas quota exceeded for the block"
+    ~description:
+      "The sum of gas consumed by all the operations in the block \
+       exceeds the hard gas limit per block"
+    empty
+    (function Block_quota_exceeded -> Some () | _ -> None)
+    (fun () -> Block_quota_exceeded) ;
diff --git a/src/proto_alpha/lib_protocol/src/gas_repr.mli b/src/proto_alpha/lib_protocol/src/gas_repr.mli
index 01a3b9dcf..e0b644426 100644
--- a/src/proto_alpha/lib_protocol/src/gas_repr.mli
+++ b/src/proto_alpha/lib_protocol/src/gas_repr.mli
@@ -9,7 +9,7 @@
 
 type t =
   | Unaccounted
-  | Limited of { remaining : int }
+  | Limited of { remaining : Z.t }
 
 val encoding : t Data_encoding.encoding
 val pp : Format.formatter -> t -> unit
@@ -19,9 +19,10 @@ type cost
 val cost_encoding : cost Data_encoding.encoding
 val pp_cost : Format.formatter -> cost -> unit
 
-type error += Quota_exceeded
+type error += Block_quota_exceeded (* `Temporary *)
+type error += Operation_quota_exceeded (* `Temporary *)
 
-val consume : t -> cost -> t tzresult
+val consume : Z.t -> t -> cost -> (Z.t * t) tzresult
 
 val free : cost
 val step_cost : int -> cost
diff --git a/src/proto_alpha/lib_protocol/src/helpers_services.ml b/src/proto_alpha/lib_protocol/src/helpers_services.ml
index 8308593a7..fbcad7506 100644
--- a/src/proto_alpha/lib_protocol/src/helpers_services.ml
+++ b/src/proto_alpha/lib_protocol/src/helpers_services.ml
@@ -52,10 +52,11 @@ module S = struct
                  (req "operation_hash" Operation_hash.encoding)
                  (req "forged_operation" bytes)
                  (opt "signature" Signature.encoding))
-      ~output: (obj1 (req "contracts" (list Contract.encoding)))
+      ~output: (obj2
+                  (req "contracts" (list Contract.encoding))
+                  (req "remaining_gas" Gas.encoding))
       RPC_path.(custom_root / "apply_operation")
 
-
   let trace_code =
     RPC_service.post_service
       ~description: "Run a piece of code in the current context, \
@@ -79,7 +80,7 @@ module S = struct
       ~query: RPC_query.empty
       ~input: (obj2
                  (req "program" Script.expr_encoding)
-                 (opt "gas" int31))
+                 (opt "gas" z))
       ~output: (obj2
                   (req "type_map" Script_tc_errors_registration.type_map_enc)
                   (req "gas" Gas.encoding))
@@ -93,7 +94,7 @@ module S = struct
       ~input: (obj3
                  (req "data" Script.expr_encoding)
                  (req "type" Script.expr_encoding)
-                 (opt "gas" int31))
+                 (opt "gas" z))
       ~output: (obj1 (req "gas" Gas.encoding))
       RPC_path.(custom_root / "typecheck_data")
 
@@ -105,7 +106,7 @@ module S = struct
       ~input: (obj3
                  (req "data" Script.expr_encoding)
                  (req "type" Script.expr_encoding)
-                 (opt "gas" int31))
+                 (opt "gas" z))
       ~output: (obj2
                   (req "hash" string)
                   (req "gas" Gas.encoding))
@@ -150,13 +151,13 @@ module I = struct
         Apply.apply_operation
           ctxt (Some baker_pkh) pred_block block_prio hash operation
         >>=? function
-        | (_ctxt, _, Some script_err) -> Lwt.return (Error script_err)
-        | (_ctxt, contracts, None) -> Lwt.return (Ok contracts)
+        | (_ctxt, _, _, Some script_err) -> Lwt.return (Error script_err)
+        | (_ctxt, gas, contracts, None) -> Lwt.return (Ok (contracts, gas))
 
 
   let run_parameters ctxt (script, storage, input, amount, contract, origination_nonce) =
     let max_gas =
-      Constants.max_gas ctxt in
+      Constants.hard_gas_limit_per_operation ctxt in
     let origination_nonce =
       match origination_nonce with
       | Some origination_nonce -> origination_nonce
@@ -178,7 +179,10 @@ let () =
   register0 S.run_code begin fun ctxt () parameters ->
     let (code, storage, input, amount, contract, gas, origination_nonce) =
       I.run_parameters ctxt parameters in
-    let ctxt = if Compare.Int.(gas > 0) then Gas.set_limit ctxt gas else Gas.set_unlimited ctxt in
+    begin if Compare.Z.(gas > Z.zero) then
+        Lwt.return (Gas.set_limit ctxt gas)
+      else
+        return (Gas.set_unlimited ctxt) end >>=? fun ctxt ->
     Script_interpreter.execute
       origination_nonce
       contract (* transaction initiator *)
@@ -191,7 +195,10 @@ let () =
   register0 S.trace_code begin fun ctxt () parameters ->
     let (code, storage, input, amount, contract, gas, origination_nonce) =
       I.run_parameters ctxt parameters in
-    let ctxt = if Compare.Int.(gas > 0) then Gas.set_limit ctxt gas else Gas.set_unlimited ctxt in
+    begin if Compare.Z.(gas > Z.zero) then
+        Lwt.return (Gas.set_limit ctxt gas)
+      else
+        return (Gas.set_unlimited ctxt) end >>=? fun ctxt ->
     Script_interpreter.trace
       origination_nonce
       contract (* transaction initiator *)
@@ -203,24 +210,24 @@ let () =
               ~f:(Script_ir_translator.to_printable_big_map ctxt))
   end ;
   register0 S.typecheck_code begin fun ctxt () (expr, maybe_gas) ->
-    let ctxt = match maybe_gas with
-      | None -> Gas.set_unlimited ctxt
-      | Some gas -> Gas.set_limit ctxt gas in
+    begin match maybe_gas with
+      | None -> return (Gas.set_unlimited ctxt)
+      | Some gas -> Lwt.return (Gas.set_limit ctxt gas) end >>=? fun ctxt ->
     Script_ir_translator.typecheck_code ctxt expr >>=? fun (res, ctxt) ->
     return (res, Gas.level ctxt)
   end ;
   register0 S.typecheck_data begin fun ctxt () (data, ty, maybe_gas) ->
-    let ctxt = match maybe_gas with
-      | None -> Gas.set_unlimited ctxt
-      | Some gas -> Gas.set_limit ctxt gas in
+    begin match maybe_gas with
+      | None -> return (Gas.set_unlimited ctxt)
+      | Some gas -> Lwt.return (Gas.set_limit ctxt gas) end >>=? fun ctxt ->
     Script_ir_translator.typecheck_data ctxt (data, ty) >>=? fun ctxt ->
     return (Gas.level ctxt)
   end ;
   register0 S.hash_data begin fun ctxt () (expr, typ, maybe_gas) ->
     let open Script_ir_translator in
-    let ctxt = match maybe_gas with
-      | None -> Gas.set_unlimited ctxt
-      | Some gas -> Gas.set_limit ctxt gas in
+    begin match maybe_gas with
+      | None -> return (Gas.set_unlimited ctxt)
+      | Some gas -> Lwt.return (Gas.set_limit ctxt gas) end >>=? fun ctxt ->
     Lwt.return (parse_ty false (Micheline.root typ)) >>=? fun (Ex_ty typ, _) ->
     parse_data ctxt typ (Micheline.root expr) >>=? fun (data, ctxt) ->
     Lwt.return (Script_ir_translator.hash_data ctxt typ data) >>=? fun (hash, ctxt) ->
@@ -343,9 +350,9 @@ module Forge = struct
 
     let transaction ctxt
         block ~branch ~source ?sourcePubKey ~counter
-        ~amount ~destination ?parameters ~fee ()=
+        ~amount ~destination ?parameters ~gas_limit ~fee ()=
       operations ctxt block ~branch ~source ?sourcePubKey ~counter ~fee
-        Alpha_context.[Transaction { amount ; parameters ; destination }]
+        Alpha_context.[Transaction { amount ; parameters ; destination ; gas_limit }]
 
     let origination ctxt
         block ~branch
@@ -353,7 +360,8 @@ module Forge = struct
         ~managerPubKey ~balance
         ?(spendable = true)
         ?(delegatable = true)
-        ?delegatePubKey ?script ~fee () =
+        ?delegatePubKey ?script
+        ~gas_limit ~fee () =
       operations ctxt block ~branch ~source ?sourcePubKey ~counter ~fee
         Alpha_context.[
           Origination { manager = managerPubKey ;
@@ -361,7 +369,8 @@ module Forge = struct
                         script ;
                         spendable ;
                         delegatable ;
-                        credit = balance }
+                        credit = balance ;
+                        gas_limit }
         ]
 
     let delegation ctxt
diff --git a/src/proto_alpha/lib_protocol/src/helpers_services.mli b/src/proto_alpha/lib_protocol/src/helpers_services.mli
index 0d8ff93d5..ba21f05b0 100644
--- a/src/proto_alpha/lib_protocol/src/helpers_services.mli
+++ b/src/proto_alpha/lib_protocol/src/helpers_services.mli
@@ -19,7 +19,7 @@ val minimal_time:
 val apply_operation:
   'a #RPC_context.simple ->
   'a -> Block_hash.t -> Operation_hash.t -> MBytes.t -> Signature.t option ->
-  (Contract.t list) shell_tzresult Lwt.t
+  (Contract.t list * Gas.t) shell_tzresult Lwt.t
 
 val run_code:
   'a #RPC_context.simple ->
@@ -37,16 +37,16 @@ val trace_code:
 
 val typecheck_code:
   'a #RPC_context.simple ->
-  'a -> (Script.expr * int option) ->
+  'a -> (Script.expr * Z.t option) ->
   (Script_tc_errors.type_map * Gas.t) shell_tzresult Lwt.t
 
 val typecheck_data:
   'a #RPC_context.simple ->
-  'a -> Script.expr * Script.expr * int option -> Gas.t shell_tzresult Lwt.t
+  'a -> Script.expr * Script.expr * Z.t option -> Gas.t shell_tzresult Lwt.t
 
 val hash_data:
   'a #RPC_context.simple ->
-  'a -> Script.expr * Script.expr * int option -> (string * Gas.t) shell_tzresult Lwt.t
+  'a -> Script.expr * Script.expr * Z.t option -> (string * Gas.t) shell_tzresult Lwt.t
 
 val level:
   'a #RPC_context.simple ->
@@ -88,6 +88,7 @@ module Forge : sig
       amount:Tez.t ->
       destination:Contract.t ->
       ?parameters:Script.expr ->
+      gas_limit:Z.t ->
       fee:Tez.t ->
       unit -> MBytes.t shell_tzresult Lwt.t
 
@@ -103,6 +104,7 @@ module Forge : sig
       ?delegatable:bool ->
       ?delegatePubKey: public_key_hash ->
       ?script:Script.t ->
+      gas_limit:Z.t ->
       fee:Tez.t->
       unit -> MBytes.t shell_tzresult Lwt.t
 
diff --git a/src/proto_alpha/lib_protocol/src/main.ml b/src/proto_alpha/lib_protocol/src/main.ml
index 50bdda574..686b93a9e 100644
--- a/src/proto_alpha/lib_protocol/src/main.ml
+++ b/src/proto_alpha/lib_protocol/src/main.ml
@@ -116,7 +116,7 @@ let apply_operation ({ mode ; ctxt ; op_count ; _ } as data) operation =
         Some baker in
   Apply.apply_operation ctxt baker pred_block block_prio
     (Alpha_context.Operation.hash operation) operation
-  >>=? fun (ctxt, _contracts, _ignored_script_error) ->
+  >>=? fun (ctxt, _gas, _contracts, _ignored_script_error) ->
   let op_count = op_count + 1 in
   return { data with ctxt ; op_count }
 
diff --git a/src/proto_alpha/lib_protocol/src/operation_repr.ml b/src/proto_alpha/lib_protocol/src/operation_repr.ml
index ac00007e3..addee206e 100644
--- a/src/proto_alpha/lib_protocol/src/operation_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/operation_repr.ml
@@ -82,6 +82,7 @@ and manager_operation =
       amount: Tez_repr.tez ;
       parameters: Script_repr.expr option ;
       destination: Contract_repr.contract ;
+      gas_limit: Z.t;
     }
   | Origination of {
       manager: Signature.Public_key_hash.t ;
@@ -90,6 +91,7 @@ and manager_operation =
       spendable: bool ;
       delegatable: bool ;
       credit: Tez_repr.tez ;
+      gas_limit: Z.t;
     }
   | Delegation of Signature.Public_key_hash.t option
 
@@ -118,47 +120,49 @@ module Encoding = struct
 
   let transaction_encoding =
     describe ~title:"Transaction operation" @@
-    obj4
+    obj5
       (req "kind" (constant "transaction"))
       (req "amount" Tez_repr.encoding)
       (req "destination" Contract_repr.encoding)
       (opt "parameters" Script_repr.expr_encoding)
+      (req "gas_limit" z)
 
   let transaction_case tag =
     case tag ~name:"Transaction" transaction_encoding
       (function
-        | Transaction { amount ; destination ; parameters } ->
-            Some ((), amount, destination, parameters)
+        | Transaction { amount ; destination ; parameters ; gas_limit } ->
+            Some ((), amount, destination, parameters, gas_limit)
         | _ -> None)
-      (fun ((), amount, destination, parameters) ->
-         Transaction { amount ; destination ; parameters })
+      (fun ((), amount, destination, parameters, gas_limit) ->
+         Transaction { amount ; destination ; parameters ; gas_limit })
 
   let origination_encoding =
     describe ~title:"Origination operation" @@
-    (obj7
+    (obj8
        (req "kind" (constant "origination"))
        (req "managerPubkey" Signature.Public_key_hash.encoding)
        (req "balance" Tez_repr.encoding)
        (opt "spendable" bool)
        (opt "delegatable" bool)
        (opt "delegate" Signature.Public_key_hash.encoding)
-       (opt "script" Script_repr.encoding))
+       (opt "script" Script_repr.encoding)
+       (req "gas_limit" z))
 
   let origination_case tag =
     case tag ~name:"Origination" origination_encoding
       (function
         | Origination { manager ; credit ; spendable ;
-                        delegatable ; delegate ; script } ->
+                        delegatable ; delegate ; script ; gas_limit } ->
             Some ((), manager, credit, Some spendable,
-                  Some delegatable, delegate, script)
+                  Some delegatable, delegate, script, gas_limit)
         | _ -> None)
-      (fun ((), manager, credit, spendable, delegatable, delegate, script) ->
+      (fun ((), manager, credit, spendable, delegatable, delegate, script, gas_limit) ->
          let delegatable =
            match delegatable with None -> true | Some b -> b in
          let spendable =
            match spendable with None -> true | Some b -> b in
          Origination
-           {manager ; credit ; spendable ; delegatable ; delegate ; script })
+           {manager ; credit ; spendable ; delegatable ; delegate ; script ; gas_limit })
 
   let delegation_encoding =
     describe ~title:"Delegation operation" @@
diff --git a/src/proto_alpha/lib_protocol/src/operation_repr.mli b/src/proto_alpha/lib_protocol/src/operation_repr.mli
index 509430a92..7ccdd287b 100644
--- a/src/proto_alpha/lib_protocol/src/operation_repr.mli
+++ b/src/proto_alpha/lib_protocol/src/operation_repr.mli
@@ -82,6 +82,7 @@ and manager_operation =
       amount: Tez_repr.tez ;
       parameters: Script_repr.expr option ;
       destination: Contract_repr.contract ;
+      gas_limit: Z.t ;
     }
   | Origination of {
       manager: Signature.Public_key_hash.t ;
@@ -90,6 +91,7 @@ and manager_operation =
       spendable: bool ;
       delegatable: bool ;
       credit: Tez_repr.tez ;
+      gas_limit: Z.t ;
     }
   | Delegation of Signature.Public_key_hash.t option
 
diff --git a/src/proto_alpha/lib_protocol/src/parameters_repr.ml b/src/proto_alpha/lib_protocol/src/parameters_repr.ml
index f0426d9e7..b7fbd945e 100644
--- a/src/proto_alpha/lib_protocol/src/parameters_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/parameters_repr.ml
@@ -27,6 +27,7 @@ let bootstrap_account_encoding =
     (fun (public_key, amount) -> { public_key ; amount })
     (tup2 Signature.Public_key.encoding Tez_repr.encoding)
 
+
 (* This encoding is used to read configuration files (e.g. sandbox.json)
    where some fields can be missing, in that case they are replaced by
    the default. *)
@@ -62,9 +63,12 @@ let constants_encoding =
        and endorsers_per_block =
          opt Compare.Int.(=)
            default.endorsers_per_block c.endorsers_per_block
-       and max_gas =
-         opt Compare.Int.(=)
-           default.max_gas c.max_gas
+       and hard_gas_limit_per_operation =
+         opt Compare.Z.(=)
+           default.hard_gas_limit_per_operation c.hard_gas_limit_per_operation
+       and hard_gas_limit_per_block =
+         opt Compare.Z.(=)
+           default.hard_gas_limit_per_block c.hard_gas_limit_per_block
        and proof_of_work_threshold =
          opt Compare.Int64.(=)
            default.proof_of_work_threshold c.proof_of_work_threshold
@@ -107,9 +111,10 @@ let constants_encoding =
           time_between_blocks,
           first_free_baking_slot,
           endorsers_per_block,
-          max_gas,
-          proof_of_work_threshold),
-        ( dictator_pubkey,
+          hard_gas_limit_per_operation,
+          hard_gas_limit_per_block),
+        ((proof_of_work_threshold,
+          dictator_pubkey,
           max_operation_data_length,
           tokens_per_roll,
           michelson_maximum_type_size,
@@ -117,8 +122,8 @@ let constants_encoding =
           origination_burn,
           block_security_deposit,
           endorsement_security_deposit,
-          block_reward,
-          endorsement_reward)))
+          block_reward),
+         (endorsement_reward))))
     (fun (( preserved_cycles,
             blocks_per_cycle,
             blocks_per_commitment,
@@ -127,9 +132,10 @@ let constants_encoding =
             time_between_blocks,
             first_free_baking_slot,
             endorsers_per_block,
-            max_gas,
-            proof_of_work_threshold),
-          ( dictator_pubkey,
+            hard_gas_limit_per_operation,
+            hard_gas_limit_per_block),
+          ((proof_of_work_threshold,
+            dictator_pubkey,
             max_operation_data_length,
             tokens_per_roll,
             michelson_maximum_type_size,
@@ -137,8 +143,8 @@ let constants_encoding =
             origination_burn,
             block_security_deposit,
             endorsement_security_deposit,
-            block_reward,
-            endorsement_reward)) ->
+            block_reward),
+           (endorsement_reward))) ->
       let unopt def = function None -> def | Some v -> v in
       let default = Constants_repr.default in
       { Constants_repr.preserved_cycles =
@@ -158,8 +164,10 @@ let constants_encoding =
           unopt default.first_free_baking_slot first_free_baking_slot ;
         endorsers_per_block =
           unopt default.endorsers_per_block endorsers_per_block ;
-        max_gas =
-          unopt default.max_gas max_gas ;
+        hard_gas_limit_per_operation =
+          unopt default.hard_gas_limit_per_operation hard_gas_limit_per_operation ;
+        hard_gas_limit_per_block =
+          unopt default.hard_gas_limit_per_block hard_gas_limit_per_block ;
         proof_of_work_threshold =
           unopt default.proof_of_work_threshold proof_of_work_threshold ;
         dictator_pubkey =
@@ -193,19 +201,22 @@ let constants_encoding =
           (opt "time_between_blocks" (list Period_repr.encoding))
           (opt "first_free_baking_slot" uint16)
           (opt "endorsers_per_block" uint16)
-          (opt "instructions_per_transaction" int31)
-          (opt "proof_of_work_threshold" int64))
-       (obj10
-          (opt "dictator_pubkey" Signature.Public_key.encoding)
-          (opt "max_operation_data_length" int31)
-          (opt "tokens_per_roll" Tez_repr.encoding)
-          (opt "michelson_maximum_type_size" uint16)
-          (opt "seed_nonce_revelation_tip" Tez_repr.encoding)
-          (opt "origination_burn" Tez_repr.encoding)
-          (opt "block_security_deposit" Tez_repr.encoding)
-          (opt "endorsement_security_deposit" Tez_repr.encoding)
-          (opt "block_reward" Tez_repr.encoding)
-          (opt "endorsement_reward" Tez_repr.encoding)))
+          (opt "hard_gas_limit_per_operation" z)
+          (opt "hard_gas_limit_per_block" z))
+       (merge_objs
+          (obj10
+             (opt "proof_of_work_threshold" int64)
+             (opt "dictator_pubkey" Signature.Public_key.encoding)
+             (opt "max_operation_data_length" int31)
+             (opt "tokens_per_roll" Tez_repr.encoding)
+             (opt "michelson_maximum_type_size" uint16)
+             (opt "seed_nonce_revelation_tip" Tez_repr.encoding)
+             (opt "origination_burn" Tez_repr.encoding)
+             (opt "block_security_deposit" Tez_repr.encoding)
+             (opt "endorsement_security_deposit" Tez_repr.encoding)
+             (opt "block_reward" Tez_repr.encoding))
+          (obj1
+             (opt "endorsement_reward" Tez_repr.encoding))))
 
 let encoding =
   let open Data_encoding in
diff --git a/src/proto_alpha/lib_protocol/src/raw_context.ml b/src/proto_alpha/lib_protocol/src/raw_context.ml
index 3b1156de7..ee7b8b7ed 100644
--- a/src/proto_alpha/lib_protocol/src/raw_context.ml
+++ b/src/proto_alpha/lib_protocol/src/raw_context.ml
@@ -19,7 +19,8 @@ type t = {
   endorsements_received: Int_set.t;
   fees: Tez_repr.t ;
   rewards: Tez_repr.t ;
-  gas: Gas_repr.t;
+  block_gas: Z.t ;
+  operation_gas: Gas_repr.t ;
 }
 
 type context = t
@@ -48,12 +49,32 @@ let add_rewards ctxt rewards =
 let get_rewards ctxt = ctxt.rewards
 let get_fees ctxt = ctxt.fees
 
-let set_gas_limit ctxt remaining = { ctxt with gas = Limited { remaining } }
-let set_gas_unlimited ctxt = { ctxt with gas = Unaccounted }
+type error += Gas_limit_too_high (* `Permanent *)
+
+let () =
+  let open Data_encoding in
+  register_error_kind
+    `Permanent
+    ~id:"gas_limit_too_high"
+    ~title: "Gas limit higher than the hard limit"
+    ~description:
+      "A transaction tried to exceed the hard limit on gas"
+    empty
+    (function Gas_limit_too_high -> Some () | _ -> None)
+    (fun () -> Gas_limit_too_high)
+
+let set_gas_limit ctxt remaining =
+  if Compare.Z.(remaining > ctxt.constants.hard_gas_limit_per_operation) then
+    error Gas_limit_too_high
+  else
+    ok { ctxt with operation_gas = Limited { remaining } }
+let set_gas_unlimited ctxt =
+  { ctxt with operation_gas = Unaccounted }
 let consume_gas ctxt cost =
-  Gas_repr.consume ctxt.gas cost >>? fun gas ->
-  ok { ctxt with gas }
-let gas_level ctxt = ctxt.gas
+  Gas_repr.consume ctxt.block_gas ctxt.operation_gas cost >>? fun (block_gas, operation_gas) ->
+  ok { ctxt with block_gas ; operation_gas }
+let gas_level ctxt = ctxt.operation_gas
+let block_gas_level ctxt = ctxt.block_gas
 
 
 type storage_error =
@@ -272,7 +293,8 @@ let prepare ~level ~timestamp ~fitness ctxt =
     endorsements_received = Int_set.empty ;
     fees = Tez_repr.zero ;
     rewards = Tez_repr.zero ;
-    gas = Unaccounted ;
+    operation_gas = Unaccounted ;
+    block_gas = constants.Constants_repr.hard_gas_limit_per_block ;
   }
 
 let check_first_block ctxt =
@@ -317,7 +339,8 @@ let register_resolvers enc resolve =
       endorsements_received = Int_set.empty ;
       fees = Tez_repr.zero ;
       rewards = Tez_repr.zero ;
-      gas = Unaccounted ;
+      block_gas = Constants_repr.default.hard_gas_limit_per_block ;
+      operation_gas = Unaccounted ;
     } in
     resolve faked_context str in
   Context.register_resolver enc  resolve
diff --git a/src/proto_alpha/lib_protocol/src/raw_context.mli b/src/proto_alpha/lib_protocol/src/raw_context.mli
index 2ef8df1ab..b5a8b0b24 100644
--- a/src/proto_alpha/lib_protocol/src/raw_context.mli
+++ b/src/proto_alpha/lib_protocol/src/raw_context.mli
@@ -73,10 +73,13 @@ val add_rewards: context -> Tez_repr.t -> context tzresult Lwt.t
 val get_fees: context -> Tez_repr.t
 val get_rewards: context -> Tez_repr.t
 
-val set_gas_limit: t -> int -> t
+type error += Gas_limit_too_high (* `Permanent *)
+
+val set_gas_limit: t -> Z.t -> t tzresult
 val set_gas_unlimited: t -> t
 val consume_gas: t -> Gas_repr.cost -> t tzresult
 val gas_level: t -> Gas_repr.t
+val block_gas_level: t -> Z.t
 
 (** {1 Generic accessors} *************************************************)
 
diff --git a/src/proto_alpha/lib_protocol/src/script_interpreter.ml b/src/proto_alpha/lib_protocol/src/script_interpreter.ml
index 8d816ed41..be0bc2f7f 100644
--- a/src/proto_alpha/lib_protocol/src/script_interpreter.ml
+++ b/src/proto_alpha/lib_protocol/src/script_interpreter.ml
@@ -791,8 +791,8 @@ let rec interp
             Lwt.return (Gas.consume ctxt Interp_costs.steps_to_quota) >>=? fun ctxt ->
             let steps = match Gas.level ctxt with
               | Limited { remaining } -> remaining
-              | Unaccounted -> max_int in
-            logged_return (Item (Script_int.(abs (of_int steps)), rest), ctxt)
+              | Unaccounted -> Z.of_string "99999999" in
+            logged_return (Item (Script_int.(abs (of_zint steps)), rest), ctxt)
         | Source (ta, tb), rest ->
             Lwt.return (Gas.consume ctxt Interp_costs.source) >>=? fun ctxt ->
             logged_return (Item ((ta, tb, orig), rest), ctxt)
diff --git a/src/proto_alpha/lib_protocol/test/helpers/helpers_apply.ml b/src/proto_alpha/lib_protocol/test/helpers/helpers_apply.ml
index e9aa80543..bf6c7fa69 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/helpers_apply.ml
+++ b/src/proto_alpha/lib_protocol/test/helpers/helpers_apply.ml
@@ -20,7 +20,7 @@ let operation
     pred_block_hash
     0
     hash
-    operation >>=? fun (tc, contracts, err) ->
+    operation >>=? fun (tc, _, contracts, err) ->
   return ((contracts, err), tc)
 
 
@@ -31,6 +31,7 @@ let transaction ~tc ?(fee = 0) ?baker
     src dst.contract
     (Helpers_cast.cents_of_int amount)
     ~fee: (Helpers_cast.cents_of_int fee)
+    (Proto_alpha.Alpha_context.Constants.hard_gas_limit_per_operation tc)
   @@ Helpers_cast.ctxt_of_tc tc
   >>=? fun protop ->
   operation ~tc ?baker ~src pbh opsh protop
@@ -45,7 +46,9 @@ let transaction_pred ?tc ~(pred: Helpers_block.result) ?baker (src, dst, amount,
 let script_origination
     ~tc pbh opsh script src amount =
   Helpers_operation.script_origination_full
-    script src (Helpers_cast.cents_of_int amount) @@ Helpers_cast.ctxt_of_tc tc
+    script src (Helpers_cast.cents_of_int amount)
+    (Proto_alpha.Alpha_context.Constants.hard_gas_limit_per_operation tc)
+  @@ Helpers_cast.ctxt_of_tc tc
   >>=? fun protop -> operation ~tc ?baker: None ~src pbh opsh protop
 
 
@@ -55,6 +58,7 @@ let origination
   Helpers_operation.origination_full
     src ~spendable ~delegatable
     (Helpers_cast.cents_of_int amount) ~fee:(Helpers_cast.tez_of_int fee)
+    (Proto_alpha.Alpha_context.Constants.hard_gas_limit_per_operation tc)
   @@ Helpers_cast.ctxt_of_tc tc
   >>=? fun protop ->
   operation ~tc ?baker ~src pbh opsh protop
diff --git a/src/proto_alpha/lib_protocol/test/helpers/helpers_operation.ml b/src/proto_alpha/lib_protocol/test/helpers/helpers_operation.ml
index d0696086f..8c4e7ba04 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/helpers_operation.ml
+++ b/src/proto_alpha/lib_protocol/test/helpers/helpers_operation.ml
@@ -32,18 +32,19 @@ let manager_full src ?(fee = Tez.zero) ops context =
   manager src ~fee ops context >>=? fun ops -> return @@ sourced ops
 
 
-let transaction ?parameters amount destination =
+let transaction ?parameters amount destination gas_limit =
   Transaction {
     amount ;
     parameters ;
-    destination
+    destination ;
+    gas_limit
   }
 
 
 let origination
     ?(delegatable = true) ?(script = None)
     ?(spendable = true) ?(delegate = None)
-    (manager: Helpers_account.t) credit
+    (manager: Helpers_account.t) credit gas_limit
   =
   Origination {
     manager = manager.hpub ;
@@ -51,7 +52,8 @@ let origination
     spendable ;
     delegatable ;
     script ;
-    credit
+    credit ;
+    gas_limit
   }
 
 
@@ -63,16 +65,16 @@ let delegation_full ?(fee = Tez.zero) src delegate context =
   manager_full src ~fee [delegation delegate] context
 
 
-let script_origination_full script src credit context =
-  manager_full src ~fee: Tez.zero [origination ~script src credit] context
+let script_origination_full script src credit gas_limit context =
+  manager_full src ~fee: Tez.zero [origination ~script src credit gas_limit] context
 
 
-let origination_full ?(spendable = true) ?(delegatable = true) ?(fee = Tez.zero) src credit context =
-  manager_full src ~fee [origination ~spendable ~delegatable src credit] context
+let origination_full ?(spendable = true) ?(delegatable = true) ?(fee = Tez.zero) src credit gas_limit context =
+  manager_full src ~fee [origination ~spendable ~delegatable src credit gas_limit] context
 
 
-let transaction_full ?(fee = Tez.zero) ?parameters src dst amount context =
-  manager src ~fee [transaction ?parameters amount dst] context
+let transaction_full ?(fee = Tez.zero) ?parameters src dst amount gas_limit context =
+  manager src ~fee [transaction ?parameters amount dst gas_limit] context
   >>=? fun manager_op ->
   return @@ sourced manager_op
 
diff --git a/src/proto_alpha/lib_protocol/test/helpers/helpers_operation.mli b/src/proto_alpha/lib_protocol/test/helpers/helpers_operation.mli
index 91f8c26cb..445f01164 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/helpers_operation.mli
+++ b/src/proto_alpha/lib_protocol/test/helpers/helpers_operation.mli
@@ -23,12 +23,12 @@ val manager_full :
   Alpha_environment.Context.t -> proto_operation proto_tzresult Lwt.t
 
 val transaction :
-  ?parameters:Script.expr -> Tez.t -> Contract.contract ->
+  ?parameters:Script.expr -> Tez.t -> Contract.contract -> Z.t ->
   manager_operation
 
 val origination :
   ?delegatable:bool -> ?script:Script.t option -> ?spendable:bool ->
-  ?delegate:public_key_hash option -> Helpers_account.t -> Tez.t -> manager_operation
+  ?delegate:public_key_hash option -> Helpers_account.t -> Tez.t -> Z.t -> manager_operation
 
 val delegation : public_key_hash -> manager_operation
 
@@ -37,16 +37,16 @@ val delegation_full :
   proto_operation proto_tzresult Lwt.t
 
 val script_origination_full :
-  Script.t option -> Helpers_account.t -> Tez.t -> Alpha_environment.Context.t ->
+  Script.t option -> Helpers_account.t -> Tez.t -> Z.t -> Alpha_environment.Context.t ->
   proto_operation proto_tzresult  Lwt.t
 
 val origination_full :
   ?spendable:bool -> ?delegatable:bool -> ?fee:Tez.tez ->
-  Helpers_account.t -> Tez.t -> Alpha_environment.Context.t ->
+  Helpers_account.t -> Tez.t -> Z.t -> Alpha_environment.Context.t ->
   proto_operation proto_tzresult Lwt.t
 
 val transaction_full :
-  ?fee:Tez.tez -> ?parameters:Proto_alpha.Alpha_context.Script.expr -> Helpers_account.t -> Contract.contract -> Tez.t ->
+  ?fee:Tez.tez -> ?parameters:Proto_alpha.Alpha_context.Script.expr -> Helpers_account.t -> Contract.contract -> Tez.t -> Z.t ->
   Alpha_environment.Context.t -> proto_operation proto_tzresult Lwt.t
 
 val amendment_operation :
diff --git a/src/proto_alpha/lib_protocol/test/helpers/helpers_script.ml b/src/proto_alpha/lib_protocol/test/helpers/helpers_script.ml
index 9c4e6983c..0d98d734e 100644
--- a/src/proto_alpha/lib_protocol/test/helpers/helpers_script.ml
+++ b/src/proto_alpha/lib_protocol/test/helpers/helpers_script.ml
@@ -21,7 +21,8 @@ let execute_code_pred
   >>=? fun ((dst, _), tc) ->
   let dst = List.hd dst in
   let ctxt = Helpers_cast.ctxt_of_tc tc in
-  Helpers_operation.transaction_full op dst Tez.zero ctxt
+  let gas = Proto_alpha.Alpha_context.Constants.hard_gas_limit_per_operation tc in
+  Helpers_operation.transaction_full op dst Tez.zero gas ctxt
   >>=? fun dummy_protop ->
   let op_header = Helpers_block.get_op_header_res pred in
   let apply_op = Helpers_operation.apply_of_proto
@@ -29,8 +30,7 @@ let execute_code_pred
   let hash = Operation.hash apply_op in
   let dummy_nonce = Contract.initial_origination_nonce hash in
   let amount = Tez.zero in
-  let gas = Proto_alpha.Alpha_context.Constants.max_gas tc in
-  let tc = Proto_alpha.Alpha_context.Gas.set_limit tc gas in
+  Lwt.return (Proto_alpha.Alpha_context.Gas.set_limit tc gas) >>=? fun tc ->
   let return = Script_interpreter.execute
       dummy_nonce op.contract dst
       tc script amount argument in
diff --git a/src/proto_alpha/lib_protocol/test/test_big_maps.ml b/src/proto_alpha/lib_protocol/test/test_big_maps.ml
index ce8870515..cad1fa241 100644
--- a/src/proto_alpha/lib_protocol/test/test_big_maps.ml
+++ b/src/proto_alpha/lib_protocol/test/test_big_maps.ml
@@ -94,9 +94,10 @@ let main () =
   debug "initial big map is ok" ;
   let call tc input result =
     Lwt.return (parse_expr input) >>=? fun parameters ->
+    let gas = Proto_alpha.Alpha_context.Constants.hard_gas_limit_per_operation tc in
     Helpers.Operation.transaction_full
       src contract (Helpers_cast.cents_of_int 100_00)
-      (Helpers_cast.ctxt_of_tc tc)
+      gas (Helpers_cast.ctxt_of_tc tc)
       ~parameters >>=?? fun op ->
     Helpers.Apply.operation ~tc
       ~src pred.Helpers_block.hash
diff --git a/src/proto_alpha/lib_protocol/test/test_michelson.ml b/src/proto_alpha/lib_protocol/test/test_michelson.ml
index e298306ac..35102de46 100644
--- a/src/proto_alpha/lib_protocol/test/test_michelson.ml
+++ b/src/proto_alpha/lib_protocol/test/test_michelson.ml
@@ -287,7 +287,7 @@ let test_example () =
   test_output ~location: __LOC__ "exec_concat" "Unit" "\"test\"" "\"test_abc\"" >>=? fun _ ->
 
   (*  Get current steps to quota *)
-  test_output ~location: __LOC__ "steps_to_quota" "Unit" "Unit" "39968" >>=? fun _ ->
+  test_output ~location: __LOC__ "steps_to_quota" "Unit" "Unit" "39989" >>=? fun _ ->
 
   let bootstrap_0 = List.nth Account.bootstrap_accounts 0 in
   get_balance_res bootstrap_0 sb >>=?? fun _balance ->