diff --git a/python/paddle_serving_client/__init__.py b/python/paddle_serving_client/__init__.py
index d9a4a3ff2d3550dfc2696c23d4ca208d8fa395dc..3fe508f707ca90d0291823d3a52e2d8dbc9fe71e 100644
--- a/python/paddle_serving_client/__init__.py
+++ b/python/paddle_serving_client/__init__.py
@@ -156,6 +156,9 @@ class Client(object):
                 key))
 
     def predict(self, feed=None, fetch=None):
+        if feed is None or fetch is None:
+            raise ValueError("You should specify feed and fetch for prediction")
+
         fetch_list = []
         if isinstance(fetch, str):
             fetch_list = [fetch]