diff --git a/tensor2tensor/data_generators/text_encoder.py b/tensor2tensor/data_generators/text_encoder.py
index 0a05cb721..e329dedc4 100644
--- a/tensor2tensor/data_generators/text_encoder.py
+++ b/tensor2tensor/data_generators/text_encoder.py
@@ -29,6 +29,7 @@
 
 import six
 from six import PY2
+from six import unichr
 from six.moves import xrange  # pylint: disable=redefined-builtin
 from tensor2tensor.data_generators import tokenizer