diff --git a/ets2panda/compiler/core/ETSGen.cpp b/ets2panda/compiler/core/ETSGen.cpp
index 9603461920f60c560ea4dc739ebc7265f423bd9a..cd29ebce8505b853dd5a3c857c919ebafcf57ee3 100644
--- a/ets2panda/compiler/core/ETSGen.cpp
+++ b/ets2panda/compiler/core/ETSGen.cpp
@@ -2324,8 +2324,11 @@ void ETSGen::StringBuilderAppend(const ir::AstNode *node, VReg builder)
         signature = Signatures::BUILTIN_STRING_BUILDER_APPEND_BUILTIN_STRING;
     }
 
-    if ((GetAccumulatorType()->IsETSObjectType() || GetAccumulatorType()->IsETSTypeParameter()) &&
-        !GetAccumulatorType()->IsETSStringType()) {
+    const checker::Type *accumulatorType = GetAccumulatorType();
+    bool isNullOrUndefined = accumulatorType->ContainsNull() || accumulatorType->ContainsUndefined();
+    bool isETSObjectOrTypeParam = accumulatorType->IsETSObjectType() || accumulatorType->IsETSTypeParameter();
+    bool isStringType = accumulatorType->IsETSStringType();
+    if (isETSObjectOrTypeParam && (!isStringType || isNullOrUndefined)) {
         if (Checker()->MayHaveNullValue(GetAccumulatorType())) {
             Label *ifnull = AllocLabel();
             Label *end = AllocLabel();
diff --git a/ets2panda/test/runtime/ets/stringConcatenation.ets b/ets2panda/test/runtime/ets/stringConcatenation.ets
new file mode 100644
index 0000000000000000000000000000000000000000..ff66d04edc5a5967d4e65bf5101872179d05987e
--- /dev/null
+++ b/ets2panda/test/runtime/ets/stringConcatenation.ets
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2024 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.
+ */
+
+function main() {
+    let src: string | undefined = undefined;
+    let s = "_str_";
+    let udef = undefined;
+    let a :string = "A_";
+    let n : string | undefined | null = null;
+
+    let dst: string = "" + src;
+    let dst_s : string = src + "";
+    let a_dst :string = a + dst;
+    let n_dst : string = n + a_dst;
+    let dst_a : string = dst + a;
+    
+    
+
+    assert dst == "undefined";
+    assert dst_s == "undefined";
+    assert a_dst == "A_undefined";
+    assert dst_a == "undefinedA_";
+    assert n_dst == "nullA_undefined";
+    assert udef + s == "undefined_str_";
+    assert s + udef == "_str_undefined";
+    assert a + n == "A_null";
+    assert a + s == "A__str_";
+    assert a + s + udef == "A__str_undefined";
+    assert a + udef + a == "A_undefinedA_";
+    assert udef + s + n == "undefined_str_null";
+
+}