diff --git a/requirements.txt b/requirements.txt
index 610dcc7..7d3279d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,7 +4,7 @@ cryptography==3.2.1
 decorator==4.4.2
 joblib==0.17.0
 networkx==2.5
-nltk==3.5
+nltk==3.6.6
 numpy==1.19.2
 pandas==1.1.3
 pycparser==2.20