diff --git a/python/examples/imagenet/resnet50_web_service.py b/python/examples/imagenet/resnet50_web_service.py
index 3966d31c951d83d8f984e5a265504035ed273125..1dbb2be90da5192baf8b274e9dd3255179842f6d 100644
--- a/python/examples/imagenet/resnet50_web_service.py
+++ b/python/examples/imagenet/resnet50_web_service.py
@@ -65,7 +65,7 @@ image_service = ImageService(name="image")
 image_service.load_model_config(sys.argv[1])
 image_service.init_imagenet_setting()
 if device == "gpu":
-    image_service.set_gpus("0,1")
+    image_service.set_gpus("0")
 image_service.prepare_server(
     workdir="workdir", port=int(sys.argv[3]), device=device)
 image_service.run_rpc_service()
diff --git a/python/paddle_serving_server_gpu/web_service.py b/python/paddle_serving_server_gpu/web_service.py
index 6750de86f1750f2ab9dc36eca9d4307f7821e2d8..2f848b1bf707aba17213d75facba6dea186a2351 100644
--- a/python/paddle_serving_server_gpu/web_service.py
+++ b/python/paddle_serving_server_gpu/web_service.py
@@ -204,4 +204,6 @@ class WebService(object):
         return feed, fetch
 
     def postprocess(self, feed=[], fetch=[], fetch_map=None):
+        for key in fetch_map.iterkeys():
+            fetch_map[key] = fetch_map[key].tolist()
         return fetch_map