diff --git a/ets2panda/checker/types/ets/etsObjectType.cpp b/ets2panda/checker/types/ets/etsObjectType.cpp
index 1d42b6745b67e535f5e49972712ccb531f04eec8..32f5f8f46fa472a34e7d0b697dacf753b205683a 100644
--- a/ets2panda/checker/types/ets/etsObjectType.cpp
+++ b/ets2panda/checker/types/ets/etsObjectType.cpp
@@ -648,15 +648,14 @@ void ETSObjectType::SubstitutePartialTypes(TypeRelation *relation, Type *other)
 void ETSObjectType::IdenticalUptoTypeArguments(TypeRelation *relation, Type *other)
 {
     relation->Result(false);
+    if (!other->IsETSObjectType() || !CheckIdenticalFlags(other->AsETSObjectType())) {
+        return;
+    }
 
     if (IsPartial()) {
         SubstitutePartialTypes(relation, other);
     }
 
-    if (!other->IsETSObjectType() || !CheckIdenticalFlags(other->AsETSObjectType())) {
-        return;
-    }
-
     // NOTE: (DZ) only both Partial types can be compatible.
     if (static_cast<bool>(static_cast<std::byte>(IsPartial()) ^
                           static_cast<std::byte>(other->AsETSObjectType()->IsPartial()))) {
diff --git a/ets2panda/test/ast/compiler/ets/union_type_of_partial_type.ets b/ets2panda/test/ast/compiler/ets/union_type_of_partial_type.ets
new file mode 100644
index 0000000000000000000000000000000000000000..b024428363cc3f69df19ac62f9c781c0332e5f3f
--- /dev/null
+++ b/ets2panda/test/ast/compiler/ets/union_type_of_partial_type.ets
@@ -0,0 +1,28 @@
+/*
+ * 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: *
+ * 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.
+ */
+
+abstract class A<T extends A<T>>{
+    foo({ }, init: Partial<T> | undefined): void {
+    }
+}
+
+/* @@? 16:9 Error SyntaxError: Unexpected token, expected an identifier. */
+/* @@? 16:9 Error SyntaxError: Parameter declaration should have an explicit type annotation. */
+/* @@? 16:9 Error SyntaxError: Unexpected token, expected ',' or ')'. */
+/* @@? 16:12 Error SyntaxError: Unexpected token ','. */
+/* @@? 16:42 Error SyntaxError: Unexpected token ')'. */
+/* @@? 16:43 Error SyntaxError: Unexpected token ':'. */
+/* @@? 16:45 Error SyntaxError: void is a predefined type, cannot be used as an identifier */
+/* @@? 16:50 Error SyntaxError: Unexpected token '{'. */
+/* @@? 18:1 Error SyntaxError: Unexpected token '}'. */