diff --git a/requirements.txt b/requirements.txt
index ebe58b1..41892fa 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,7 +7,7 @@ lunr==0.5.6
 Markdown==3.2.2
 MarkupSafe==1.1.1
 mkdocs==1.1
-nltk==3.5
+nltk==3.6.6
 PyYAML==5.4
 regex==2020.5.7
 six==1.14.0