diff --git a/src/openai/_exceptions.py b/src/openai/_exceptions.py
index 7a30e4a336..17e89e8f2f 100644
--- a/src/openai/_exceptions.py
+++ b/src/openai/_exceptions.py
@@ -69,7 +69,8 @@ def __init__(self, message: str, request: httpx2.Request, *, body: object | None
         self.body = body
 
         if is_dict(body):
-            self.code = cast(Any, construct_type(type_=Optional[str], value=body.get("code")))
+            code = body.get("code")
+            self.code = str(code) if code is not None else None
             self.param = cast(Any, construct_type(type_=Optional[str], value=body.get("param")))
             self.type = cast(Any, construct_type(type_=str, value=body.get("type")))
         else:
diff --git a/tests/test_client.py b/tests/test_client.py
index 7fa7ee31bd..3281add6d2 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -123,6 +123,40 @@ def _get_open_connections(client: OpenAI | AsyncOpenAI) -> int:
 
 
 class TestOpenAI:
+    @pytest.mark.parametrize(
+        "code_fields,expected_code",
+        [
+            ({"code": 404}, "404"),
+            ({"code": 0}, "0"),
+            ({"code": "invalid_request"}, "invalid_request"),
+            ({"code": ""}, ""),
+            ({"code": None}, None),
+            ({}, None),
+        ],
+    )
+    @pytest.mark.respx2(base_url=base_url)
+    def test_api_error_code_is_string(
+        self,
+        code_fields: dict[str, object],
+        expected_code: str | None,
+        respx2_mock: MockRouter,
+        client: OpenAI,
+    ) -> None:
+        body = {"message": "Example error", "type": "invalid_request_error", "param": "model", **code_fields}
+        response = httpx2.Response(400, json={"error": body})
+        respx2_mock.get("/foo").mock(return_value=response)
+
+        with pytest.raises(APIStatusError) as exc_info:
+            client.get("/foo", cast_to=httpx2.Response)
+
+        error = exc_info.value
+        assert error.code == expected_code
+        assert error.body == body
+        assert error.response.json() == {"error": body}
+        assert error.status_code == 400
+        assert error.type == "invalid_request_error"
+        assert error.param == "model"
+
     @pytest.mark.respx2(base_url=base_url)
     def test_raw_response(self, respx2_mock: MockRouter, client: OpenAI) -> None:
         respx2_mock.post("/foo").mock(return_value=httpx2.Response(200, json={"foo": "bar"}))
@@ -1454,6 +1488,40 @@ def test_copy_auth(self) -> None:
 
 
 class TestAsyncOpenAI:
+    @pytest.mark.parametrize(
+        "code_fields,expected_code",
+        [
+            ({"code": 404}, "404"),
+            ({"code": 0}, "0"),
+            ({"code": "invalid_request"}, "invalid_request"),
+            ({"code": ""}, ""),
+            ({"code": None}, None),
+            ({}, None),
+        ],
+    )
+    @pytest.mark.respx2(base_url=base_url)
+    async def test_api_error_code_is_string(
+        self,
+        code_fields: dict[str, object],
+        expected_code: str | None,
+        respx2_mock: MockRouter,
+        async_client: AsyncOpenAI,
+    ) -> None:
+        body = {"message": "Example error", "type": "invalid_request_error", "param": "model", **code_fields}
+        response = httpx2.Response(400, json={"error": body})
+        respx2_mock.get("/foo").mock(return_value=response)
+
+        with pytest.raises(APIStatusError) as exc_info:
+            await async_client.get("/foo", cast_to=httpx2.Response)
+
+        error = exc_info.value
+        assert error.code == expected_code
+        assert error.body == body
+        assert error.response.json() == {"error": body}
+        assert error.status_code == 400
+        assert error.type == "invalid_request_error"
+        assert error.param == "model"
+
     @pytest.mark.respx2(base_url=base_url)
     async def test_raw_response(self, respx2_mock: MockRouter, async_client: AsyncOpenAI) -> None:
         respx2_mock.post("/foo").mock(return_value=httpx2.Response(200, json={"foo": "bar"}))