diff --git a/ets2panda/compiler/lowering/ets/unboxLowering.cpp b/ets2panda/compiler/lowering/ets/unboxLowering.cpp
index 2ad5b19d6968247440f6ae5859b1fe17543e5c82..7dc46f5b7a22e1ec64d4fd1a6eabe169dbc9e702 100644
--- a/ets2panda/compiler/lowering/ets/unboxLowering.cpp
+++ b/ets2panda/compiler/lowering/ets/unboxLowering.cpp
@@ -1354,7 +1354,13 @@ struct UnboxVisitor : public ir::visitor::EmptyAstVisitor {
             ReplaceInParent(nnexpr, nnexpr->Expr());
             return;
         }
-        nnexpr->SetTsType(uctx_->checker->GetNonNullishType(nnexpr->Expr()->TsType()));
+
+        // Keep the behavior consistent with Check(ir::TSNonNullExpression *expr)
+        // If the actual [smart] type is definitely 'null' or 'undefined', throw a warning and return originalType
+        auto *exprType =
+            nnexpr->Expr()->TsType()->DefinitelyETSNullish() ? nnexpr->Check(uctx_->checker) : nnexpr->Expr()->TsType();
+
+        nnexpr->SetTsType(uctx_->checker->GetNonNullishType(exprType));
         nnexpr->SetOriginalType(nnexpr->TsType());
     }
 
diff --git a/ets2panda/test/runtime/ets/non_null_expr_null.ets b/ets2panda/test/runtime/ets/non_null_expr_null.ets
new file mode 100644
index 0000000000000000000000000000000000000000..abb55e298bd8eb9fa8b66023bddf1c319399f15c
--- /dev/null
+++ b/ets2panda/test/runtime/ets/non_null_expr_null.ets
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2025 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+class A {
+    field: string = ""
+    testNonNullExpr(): string {
+        let test: A | null = null;
+        try {
+            let field = test!.field;
+        } catch (error) {
+            return "Error"
+        }
+        return "Succ"
+    }
+    testNonNullExpr2(): string {
+        let test: A | undefined = undefined;
+        try {
+            let field = test!.field;
+        } catch (error) {
+            return "Error"
+        }
+        return "Succ"
+    }
+}
+
+function main() {
+    let a = new A();
+    let result = a.testNonNullExpr();
+    arktest.assertEQ(result, "Error");
+
+    let result2 = a.testNonNullExpr2();
+    arktest.assertEQ(result2, "Error");
+}