diff --git a/requirements.txt b/requirements.txt
index 2021887616..7e5d3aab24 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -32,7 +32,7 @@ jsonschema==2.5.1
 lxml==3.6.0
 Markdown==2.6.6
 mock==2.0.0
-nltk==3.2.1
+nltk==3.6.6
 numpy==1.13.1
 oauth==1.0.1
 oauthlib==1.1.1