diff --git a/requirements.txt b/requirements.txt
old mode 100755
new mode 100644
index df82c2f..5fca1e8
--- a/requirements.txt
+++ b/requirements.txt
@@ -58,7 +58,7 @@ murmurhash==0.28.0
 nbconvert==5.3.1
 nbformat==4.4.0
 networkx==2.1
-nltk==3.2.5
+nltk==3.4.5
 nose==1.3.7
 nose-timer==0.7.1
 notebook==5.4.1