diff --git a/python/paddle/fluid/tests/unittests/test_imperative_ptb_rnn.py b/python/paddle/fluid/tests/unittests/test_imperative_ptb_rnn.py
index acf758bc28a7fe148a160a09742778bdd8446ab7..0595315f30cf38c32d8b33139caffc909d6d99b4 100644
--- a/python/paddle/fluid/tests/unittests/test_imperative_ptb_rnn.py
+++ b/python/paddle/fluid/tests/unittests/test_imperative_ptb_rnn.py
@@ -16,6 +16,7 @@ from __future__ import print_function
 
 import unittest
 import paddle.fluid as fluid
+import paddle.fluid.core as core
 from paddle.fluid.dygraph.nn import Embedding
 import paddle.fluid.framework as framework
 from paddle.fluid.optimizer import SGDOptimizer