diff --git a/lib_node_shell/state.ml b/lib_node_shell/state.ml
index 19aec3435..a18956079 100644
--- a/lib_node_shell/state.ml
+++ b/lib_node_shell/state.ml
@@ -150,7 +150,7 @@ type t = global_state
 
 module Locked_block = struct
 
-  let store_genesis store genesis commit =
+  let store_genesis store genesis context =
     let shell : Block_header.shell_header = {
       level = 0l ;
       proto_level = 0 ;
@@ -162,8 +162,8 @@ module Locked_block = struct
     } in
     let header : Block_header.t = { shell ; proto = MBytes.create 0 } in
     Store.Block.Contents.store (store, genesis.block)
-      { Store.Block.header ; message = "Genesis" ;
-        max_operations_ttl = 0 ; context = commit ;
+      { Store.Block.header ; message = Some "Genesis" ;
+        max_operations_ttl = 0 ; context ;
         max_number_of_operations = [];
         max_operation_data_length = 0;
       } >>= fun () ->
@@ -442,19 +442,11 @@ module Block = struct
 
   let store
       net_state block_header operations
-      { Updater.context ; fitness ; message ; max_operations_ttl ;
+      { Updater.context ; message ; max_operations_ttl ;
         max_number_of_operations ; max_operation_data_length } =
     let bytes = Block_header.to_bytes block_header in
     let hash = Block_header.hash_raw bytes in
     (* let's the validator check the consistency... of fitness, level, ... *)
-    let message =
-      match message with
-      | Some message -> message
-      | None ->
-          Format.asprintf "%a(%ld): %a"
-            Block_hash.pp_short hash
-            block_header.shell.level
-            Fitness.pp fitness in
     Shared.use net_state.block_store begin fun store ->
       Store.Block.Invalid_block.known store hash >>= fun known_invalid ->
       fail_when known_invalid (failure "Known invalid") >>=? fun () ->
@@ -463,7 +455,7 @@ module Block = struct
         return None
       else begin
         Context.commit
-          ~time:block_header.shell.timestamp ~message context >>= fun commit ->
+          ~time:block_header.shell.timestamp ?message context >>= fun commit ->
         let contents = {
           Store.Block.header = block_header ;
           message ;
diff --git a/lib_node_shell/state.mli b/lib_node_shell/state.mli
index 24a28c80e..d341410fe 100644
--- a/lib_node_shell/state.mli
+++ b/lib_node_shell/state.mli
@@ -129,7 +129,7 @@ module Block : sig
   val net_id: t -> Net_id.t
   val net_state: t -> Net.t
   val level: t -> Int32.t
-  val message: t -> string
+  val message: t -> string option
   val max_operations_ttl: t -> int
   val max_number_of_operations: t -> int list
   val max_operation_data_length: t -> int
diff --git a/lib_storage/context.ml b/lib_storage/context.ml
index 087246dc7..20c9ebe20 100644
--- a/lib_storage/context.ml
+++ b/lib_storage/context.ml
@@ -111,14 +111,14 @@ let checkout_exn index key =
   | Some p -> Lwt.return p
 
 
-let raw_commit ~time ~message context =
+let raw_commit ~time ?(message = "") context =
   let info =
     Irmin.Info.v ~date:(Time.to_seconds time) ~author:"Tezos" message in
   GitStore.Commit.v
     context.index.repo ~info ~parents:context.parents context.tree
 
-let commit ~time ~message context =
-  raw_commit ~time ~message context >>= fun commit ->
+let commit ~time ?message context =
+  raw_commit ~time ?message context >>= fun commit ->
   Lwt.return (GitStore.Commit.hash commit)
 
 (*-- Generic Store Primitives ------------------------------------------------*)
diff --git a/lib_storage/context.mli b/lib_storage/context.mli
index a37a951c1..a7d9b1c4b 100644
--- a/lib_storage/context.mli
+++ b/lib_storage/context.mli
@@ -61,7 +61,7 @@ val checkout: index -> Context_hash.t -> context option Lwt.t
 val checkout_exn: index -> Context_hash.t -> context Lwt.t
 val commit:
   time:Time.t ->
-  message:string ->
+  ?message:string ->
   context ->
   Context_hash.t Lwt.t
 val set_head: index -> Net_id.t -> Context_hash.t -> unit Lwt.t
diff --git a/lib_storage/store.ml b/lib_storage/store.ml
index bec45061a..36eb6c6a9 100644
--- a/lib_storage/store.ml
+++ b/lib_storage/store.ml
@@ -82,7 +82,7 @@ module Block = struct
 
   type contents = {
     header: Block_header.t ;
-    message: string ;
+    message: string option ;
     max_operations_ttl: int ;
     max_number_of_operations: int list;
     max_operation_data_length: int;
@@ -111,7 +111,7 @@ module Block = struct
                  max_number_of_operations ; max_operation_data_length ;
                  context })
              (obj6
-                (req "message" string)
+                (opt "message" string)
                 (req "max_operations_ttl" uint16)
                 (req "max_number_of_operations" (list uint16))
                 (req "max_operation_data_length" uint16)
diff --git a/lib_storage/store.mli b/lib_storage/store.mli
index f9209f0a3..2e7e6ad03 100644
--- a/lib_storage/store.mli
+++ b/lib_storage/store.mli
@@ -86,7 +86,7 @@ module Block : sig
 
   type contents = {
     header: Block_header.t ;
-    message: string ;
+    message: string option ;
     max_operations_ttl: int ;
     max_number_of_operations: int list;
     max_operation_data_length: int;
diff --git a/test/shell/test_store.ml b/test/shell/test_store.ml
index e4d25304b..4fc9cfadd 100644
--- a/test/shell/test_store.ml
+++ b/test/shell/test_store.ml
@@ -87,7 +87,7 @@ let lolblock ?(operations = []) header =
         proto = MBytes.of_string header ;
       } ;
     max_operations_ttl = 0 ;
-    message = "" ;
+    message = None ;
     context = Context_hash.zero ;
     max_number_of_operations = [] ;
     max_operation_data_length = 0 ;