diff --git a/requirements.txt b/requirements.txt
index ccd2392cf..a8f4899a1 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -72,7 +72,7 @@ mongoengine==0.15.0
 monotonic==1.5
 msrest==0.6.1
 msrestazure==0.5.0
-nltk==3.3
+nltk==3.4.5
 numpy==1.14.3
 oauth2client==4.1.2
 oauthlib==2.1.0