diff --git a/requirements.txt b/requirements.txt
index ebe9ddc..1160faa 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -43,7 +43,7 @@ nb-conda-kernels==2.2.2
 nbconvert==5.5.0
 nbformat==4.4.0
 networkx==2.3
-nltk==3.4.5
+nltk==3.6.6
 nose==1.3.7
 notebook==6.1.5
 numpy==1.17.0