diff --git a/requirements.txt b/requirements.txt
index ad8a26c..1a6eb6c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,6 @@
 jupyter
 jupyter-notebook
-nltk==3.4.5
+nltk==3.9
 numpy==1.17.2
 scikit-learn==0.21.3
 pandas==0.25.1