diff --git a/requirements.txt b/requirements.txt
index 7bfc206..feebfa4 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -87,7 +87,7 @@ navigator-updater==0.2.1
 nbconvert==5.3.1
 nbformat==4.4.0
 networkx==1.11
-nltk==3.3
+nltk==3.4.5
 nose==1.3.7
 notebook==5.5.0
 numba==0.38.0