diff --git a/ets2panda/checker/ets/utilityTypeHandlers.cpp b/ets2panda/checker/ets/utilityTypeHandlers.cpp
index 3bc326155822b3d444b65c31076f1d1d42cf44ae..973ded1928ce249789c41be09b3a80ee79717a65 100644
--- a/ets2panda/checker/ets/utilityTypeHandlers.cpp
+++ b/ets2panda/checker/ets/utilityTypeHandlers.cpp
@@ -543,6 +543,7 @@ static void SetupFunctionParams(ir::ScriptFunction *function, varbinder::Functio
                         checker->ProgramAllocator()->Adapter()),
                     checker->ProgramAllocator());
             paramExpr->Ident()->SetTsTypeAnnotation(unionType);
+            ES2PANDA_ASSERT(unionType != nullptr);
             unionType->SetParent(paramExpr->Ident());
         }
         auto [paramVar, node] = paramScope->AddParamDecl(checker->ProgramAllocator(), checker->VarBinder(), paramExpr);