diff --git a/requirements.txt b/requirements.txt
index 642f261..4a53c2c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -93,7 +93,7 @@ navigator-updater==0.2.1
 nbconvert==5.4.1
 nbformat==4.4.0
 networkx==2.2
-nltk==3.4.5
+nltk==3.6.6
 nose==1.3.7
 notebook==5.7.8
 numba==0.43.1