diff --git a/spacy/serialize/huffman.pyx b/spacy/serialize/huffman.pyx
index 1bed83d74..099510ec2 100644
--- a/spacy/serialize/huffman.pyx
+++ b/spacy/serialize/huffman.pyx
@@ -1,4 +1,5 @@
 # cython: profile=True
+from __future__ import unicode_literals
 cimport cython
 from libcpp.queue cimport priority_queue
 from libcpp.pair cimport pair