diff --git a/requirements.txt b/requirements.txt
index b547ff1..35f5b7f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,6 @@
 h5py==2.7.0
 numpy==1.16.2
-nltk==3.4.5
+nltk==3.9
 jsonlines==1.2.0
 torch==0.4.1
 gensim==3.4.0