diff --git a/requirements.txt b/requirements.txt
index a249806..8de06a7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -83,7 +83,7 @@ navigator-updater==0.1.0
 nbconvert==5.3.1
 nbformat==4.4.0
 networkx==2.0
-nltk==3.2.4
+nltk==3.6.3
 nose==1.3.7
 notebook==5.0.0
 numba==0.35.0+6.gaa35fb1