diff --git a/requirements.txt b/requirements.txt
index b840601..887cb8b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-nltk==3.2
+nltk==3.4.5
 numpy==1.10.4
 scipy==0.17.0
 python-crfsuite==0.8.4