diff --git a/requirements.txt b/requirements.txt
index e1715c2..d395b80 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,7 +5,7 @@ grpcio==1.22.0
 kiwisolver==1.1.0
 Markdown==3.1.1
 matplotlib==3.1.1
-nltk==3.4.4
+nltk==3.6.3
 numpy==1.15.0
 Pillow==6.1.0
 pkg-resources==0.0.0