diff --git a/requirements.txt b/requirements.txt
index a772ac9a3..a1742ab3a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -6,6 +6,6 @@ scipy==1.0.0
 tensorboardX==1.1
 Unidecode==1.0.22
 pillow
-nltk==3.4.5
+nltk==3.6.6
 jamo==0.4.1
 music21