diff --git a/requirements.txt b/requirements.txt
index 2f5373b..48dfa51 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -104,7 +104,7 @@ navigator-updater==0.2.1
 nbconvert==5.5.0
 nbformat==4.4.0
 networkx==2.2
-nltk==3.4
+nltk==3.6.3
 nose==1.3.7
 notebook==5.7.4
 numba==0.42.0