diff --git a/requirements.txt b/requirements.txt
index 3e85e66..b4e78b9 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -44,7 +44,7 @@ matplotlib==2.0.0
 mccabe==0.6.1
 monotonic==1.3
 mpmath==0.19
-nltk==3.2.2
+nltk==3.6.3
 numpy==1.12.0
 olefile==0.44
 pathspec==0.5.0