diff --git a/requirements.txt b/requirements.txt
index 11b32d2..d9fb3b8 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -10,7 +10,7 @@ MarkupSafe==1.1.1
 mkdocs==1.1
 mkdocs-material==4.6.3
 mkdocs-minify-plugin==0.2.3
-nltk==3.4.5
+nltk==3.6.6
 Pygments==2.5.2
 pymdown-extensions==6.3
 PyYAML==5.3