diff --git a/python/paddle_serving_client/__init__.py b/python/paddle_serving_client/__init__.py
index e5f9d62d14e0e9813fce89f0e0ee3c092cb67704..98dd32e49b8320d3f2fc3be2e7faa4b4cc9aa1b8 100644
--- a/python/paddle_serving_client/__init__.py
+++ b/python/paddle_serving_client/__init__.py
@@ -215,6 +215,9 @@ class Client(object):
             float_slot_batch, float_feed_names, int_slot_batch, int_feed_names,
             fetch_names, result_batch, self.pid)
 
+        if res == -1:
+            return None
+
         result_map_batch = []
         result_map = {}
         for i, name in enumerate(fetch_names):