diff --git a/requirements.txt b/requirements.txt
index 1a9df57..9a8589c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,7 +1,7 @@
 absl-py
 easydict
 cython
-nltk==3.4.5
+nltk==3.9.4
 numpy>=1.16.0
 sklearn
 six>=1.12.0