diff --git a/lib/src/server/handler.dart b/lib/src/server/handler.dart
index 038d969..0d27f7a 100644
--- a/lib/src/server/handler.dart
+++ b/lib/src/server/handler.dart
@@ -293,7 +293,8 @@ class ServerHandler_ extends ServiceCall {
     _customTrailers = null;
     outgoingTrailersMap['grpc-status'] = status.toString();
     if (message != null) {
-      outgoingTrailersMap['grpc-message'] = message;
+      outgoingTrailersMap['grpc-message'] =
+          Uri.encodeFull(message).replaceAll("%20", " ");
     }
 
     final outgoingTrailers = <Header>[];
diff --git a/test/server_test.dart b/test/server_test.dart
index a28698c..c9fd0eb 100644
--- a/test/server_test.dart
+++ b/test/server_test.dart
@@ -167,6 +167,20 @@ void main() {
     await harness.fromServer.done;
   });
 
+  test('Server returns encoded error for unary call', () async {
+    Future<int> methodHandler(ServiceCall call, Future<int> request) async {
+      throw GrpcError.unknown("エラー");
+    }
+
+    harness
+      ..service.unaryHandler = methodHandler
+      ..expectErrorResponse(StatusCode.unknown, '%E3%82%A8%E3%83%A9%E3%83%BC')
+      ..sendRequestHeader('/Test/Unary')
+      ..sendData(dummyValue)
+      ..toServer.close();
+    await harness.fromServer.done;
+  });
+
   test('Server returns error if multiple headers are received for unary call',
       () async {
     harness