diff --git a/requirements.txt b/requirements.txt
index daf332e..634f3c4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -37,7 +37,7 @@ matplotlib==2.1.1
 more-itertools==4.1.0
 ndg-httpsclient==0.4.4
 networkx==2.0
-nltk==3.1
+nltk==3.4.5
 numpy==1.13.1
 oauthlib==1.0.3
 opencv-python==3.4.0.12