diff --git a/requirements.txt b/requirements.txt
index 7e73197..a6b9308 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,5 +3,5 @@ gunicorn==19.9.0
 numpy==1.16.2
 pandas==0.24.2
 scikit-learn==0.20.4
-nltk==3.4
+nltk==3.6.6