diff --git a/python/paddle/fluid/layers/nn.py b/python/paddle/fluid/layers/nn.py
index 42a9f9b0a1eb7e36ce351cead9ccb6280c700e86..78cc4e9a1dff19ed3e345acb4a594506aa7ecc9b 100644
--- a/python/paddle/fluid/layers/nn.py
+++ b/python/paddle/fluid/layers/nn.py
@@ -18,6 +18,7 @@ All layers just related to the neural network.
 from __future__ import print_function
 
 import numpy as np
+import warnings
 import six
 import os
 import inspect