diff --git a/jerry-core/ecma/base/ecma-helpers.c b/jerry-core/ecma/base/ecma-helpers.c
index e7288f59978cb189044b8fdfee3d340f9793e286..ebd95c1228bb79a746deac3a4295396b3c084588 100644
--- a/jerry-core/ecma/base/ecma-helpers.c
+++ b/jerry-core/ecma/base/ecma-helpers.c
@@ -273,6 +273,11 @@ ecma_get_lex_env_type (const ecma_object_t *object_p) /**< lexical environment *
   JERRY_ASSERT (object_p != NULL);
   JERRY_ASSERT (ecma_is_lexical_environment (object_p));
 
+  if (object_p == NULL)
+  {
+    jerry_fatal(ERR_FAILED_INTERNAL_ASSERTION);
+  }
+
   return (ecma_lexical_environment_type_t) (object_p->type_flags_refs & ECMA_OBJECT_TYPE_MASK);
 } /* ecma_get_lex_env_type */