diff --git a/requirements.txt b/requirements.txt
old mode 100755
new mode 100644
index 319f5a3..e3e90e1
--- a/requirements.txt
+++ b/requirements.txt
@@ -146,7 +146,7 @@ murmurhash==1.0.1
 nbconvert==5.4.0
 nbformat==4.4.0
 networkx==2.2
-nltk==3.4
+nltk==3.6.3
 notebook==5.7.2
 numpy==1.17.2
 oauth2client==4.1.3