diff --git a/Python/Flask/FlaskIntroduction/requirements.txt b/Python/Flask/FlaskIntroduction/requirements.txt
index 30ee4285c8..a17b71ff48 100644
--- a/Python/Flask/FlaskIntroduction/requirements.txt
+++ b/Python/Flask/FlaskIntroduction/requirements.txt
@@ -347,7 +347,7 @@ nbconvert==5.6.1
 nbformat==5.0.6
 ndg-httpsclient==0.5.1
 netaddr==0.7.20
-nltk==3.5
+nltk==3.6.6
 nodeenv==1.3.5
 nose==1.3.7
 notebook==6.0.3