diff --git a/paddlespeech/server/restful/request.py b/paddlespeech/server/restful/request.py
index b7a32481f..068694de3 100644
--- a/paddlespeech/server/restful/request.py
+++ b/paddlespeech/server/restful/request.py
@@ -65,7 +65,7 @@ class TTSRequest(BaseModel):
     speed: float = 1.0
     volume: float = 1.0
     sample_rate: int = 0
-    save_path: str = None
+    save_path: Optional[str] = None
 
 
 #****************************************************************************************/
diff --git a/paddlespeech/server/restful/response.py b/paddlespeech/server/restful/response.py
index 3d991de43..12b264c02 100644
--- a/paddlespeech/server/restful/response.py
+++ b/paddlespeech/server/restful/response.py
@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 from typing import List
+from typing import Optional
 
 from pydantic import BaseModel
 
@@ -62,7 +63,7 @@ class TTSResult(BaseModel):
     volume: float = 1.0
     sample_rate: int
     duration: float
-    save_path: str = None
+    save_path: Optional[str] = None
     audio: str