diff --git a/ets2panda/compiler/lowering/ets/unboxLowering.cpp b/ets2panda/compiler/lowering/ets/unboxLowering.cpp
index 29e8d1f3755d9963f3bca943197a53a019fe4372..7c5570d7aa03baf4c309eaaddd55b7938f9ca519 100644
--- a/ets2panda/compiler/lowering/ets/unboxLowering.cpp
+++ b/ets2panda/compiler/lowering/ets/unboxLowering.cpp
@@ -753,9 +753,11 @@ struct UnboxVisitor : public ir::visitor::EmptyAstVisitor {
                 break;
             }
         }
-        ES2PANDA_ASSERT(nearestScriptFunction != nullptr);
 
-        retStmt->SetArgument(AdjustType(uctx_, retStmt->Argument(), nearestScriptFunction->Signature()->ReturnType()));
+        if (nearestScriptFunction != nullptr && retStmt != nullptr) {
+            retStmt->SetArgument(
+                AdjustType(uctx_, retStmt->Argument(), nearestScriptFunction->Signature()->ReturnType()));
+        }
     }
 
     void VisitIfStatement(ir::IfStatement *ifStmt) override
diff --git a/ets2panda/test/tsconfig/test-decl/typecheck-decl/expected.json b/ets2panda/test/tsconfig/test-decl/typecheck-decl/expected.json
index 49f23180a3e6a7c6ac3421a36a9a1d2dfb3be958..c11295340f2ad403bac9b1a921451118c5e12ebc 100644
--- a/ets2panda/test/tsconfig/test-decl/typecheck-decl/expected.json
+++ b/ets2panda/test/tsconfig/test-decl/typecheck-decl/expected.json
@@ -1,5 +1,5 @@
 {
     "returncode": 1,
-    "stdout": "TypeError: Type 'int' is not compatible with type 'String' at property 'location' [main.ets:19:28]\nTypeError: Bad operand type, the types of the operands must be numeric, same enumeration, or boolean type. [main.ets:21:9]\n",
+    "stdout": "TypeError: Type 'Int' is not compatible with type 'String' at property 'location' [main.ets:19:28]\nTypeError: Operator '!=' cannot be applied to types 'String' and 'Int'. [main.ets:21:9]\n",
     "stderr": ""
 }
\ No newline at end of file