diff --git a/requirements.txt b/requirements.txt
index d9554d1..437596b 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,7 @@ django==1.11.29
 elasticsearch-dsl>=5.0.0,<6.0.0
 jupyter==1.0.0
 mysqlclient==1.3.10
-nltk==3.4.5
+nltk==3.9
 numpy==1.12.1
 pandas==0.20.1
 requests==2.20.0