diff --git a/requirements.txt b/requirements.txt
index c24862f..25a7da7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -14,7 +14,7 @@ MarkupSafe==0.23
 matplotlib==1.5.1
 mpmath==0.19
 networkx==1.11
-nltk==3.2.1
+nltk==3.4.5
 numpy==1.11.1
 numpydoc==0.6.0
 pandas==0.21.0