diff --git a/python/paddle/v2/framework/tests/test_rowwise_add_op.py b/python/paddle/v2/framework/tests/test_rowwise_add_op.py
index 1b27f54f15..8118d2d741 100644
--- a/python/paddle/v2/framework/tests/test_rowwise_add_op.py
+++ b/python/paddle/v2/framework/tests/test_rowwise_add_op.py
@@ -23,7 +23,7 @@ class RowwiseAddGradOpTest(GradientChecker):
             "X": np.random.uniform(0.1, 1, [10, 10]).astype("float32"),
             "b": np.random.uniform(0.1, 1, [10, 1]).astype("float32")
         }
-        self.check_grad(op, inputs, set("X", "b"), "Out")
+        self.check_grad(op, inputs, set(["X", "b"]), "Out")
 
 
 #TODO(dzh): rowwise_grad check