diff --git a/requirements.txt b/requirements.txt
index 94679ed..5e0724a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -42,7 +42,7 @@ mistune==0.8.4
 murmurhash==1.0.2
 nbconvert==5.6.0
 nbformat==4.4.0
-nltk==3.4.5
+nltk==3.6.6
 notebook==6.0.1
 numpy==1.17.2
 pandas==0.25.1