diff --git a/requirements.txt b/requirements.txt
index 28290f5..76f5a4b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -85,7 +85,7 @@ multipledispatch==0.5.0
 nbconvert==5.3.1
 nbformat==4.4.0
 networkx==2.1
-nltk==3.3
+nltk==3.4.5
 nose==1.3.7
 notebook==5.5.0
 numba==0.38.0