diff --git a/src/bin/expect_tests/failwith_tests.ml b/src/bin/expect_tests/failwith_tests.ml
new file mode 100644
index 000000000..d957f03c0
--- /dev/null
+++ b/src/bin/expect_tests/failwith_tests.ml
@@ -0,0 +1,36 @@
+open Cli_expect
+
+let contract basename =
+  "../../test/contracts/" ^ basename
+let bad_contract basename =
+  "../../test/contracts/negative/" ^ basename
+
+let%expect_test _ =
+  run_ligo_good [ "run-function" ; contract "failwith.ligo" ; "failer" ; "1" ] ;
+  [%expect {|
+    failwith("some_string") |}];
+
+  run_ligo_good [ "run-function" ; contract "failwith.ligo" ; "failer" ; "1" ; "--format=json" ] ;
+  [%expect {|
+    {"status":"ok","content":"failwith(\"some_string\")"} |}];
+
+
+  run_ligo_good [ "dry-run" ; contract "subtle_nontail_fail.mligo" ; "main" ; "()" ; "()" ] ;
+  [%expect {|
+    failwith("This contract always fails") |}];
+
+  run_ligo_good [ "interpret" ; "assert(1=1)" ; "--syntax=pascaligo" ] ;
+  [%expect {|
+    Unit |}];
+
+  run_ligo_good [ "interpret" ; "assert(1=2)" ; "--syntax=pascaligo" ] ;
+  [%expect {|
+    failwith("failed assertion") |}];
+
+  run_ligo_good [ "interpret" ; "assert(1=1)" ; "--syntax=cameligo" ] ;
+  [%expect {|
+    Unit |}];
+
+  run_ligo_good [ "interpret" ; "assert(1=2)" ; "--syntax=cameligo" ] ;
+  [%expect {|
+    failwith("failed assertion") |}];
diff --git a/src/passes/operators/operators.ml b/src/passes/operators/operators.ml
index 142c3d087..be1196ad1 100644
--- a/src/passes/operators/operators.ml
+++ b/src/passes/operators/operators.ml
@@ -66,7 +66,7 @@ module Simplify = struct
   module Pascaligo = struct
 
     let constants = function
-      | "get_force"       -> ok C_MAP_FIND
+      | "assert"          -> ok C_ASSERTION
       | "get_chain_id"    -> ok C_CHAIN_ID
       | "transaction"     -> ok C_CALL
       | "get_contract"    -> ok C_CONTRACT
@@ -106,6 +106,7 @@ module Simplify = struct
       | "list_iter"       -> ok C_LIST_ITER
       | "list_fold"       -> ok C_LIST_FOLD
       | "list_map"        -> ok C_LIST_MAP
+      | "get_force"       -> ok C_MAP_FIND
       | "map_iter"        -> ok C_MAP_ITER
       | "map_map"         -> ok C_MAP_MAP
       | "map_fold"        -> ok C_MAP_FOLD