diff --git a/aws-aggregator/requirements.txt b/aws-aggregator/requirements.txt
index c945c48..66cedf3 100644
--- a/aws-aggregator/requirements.txt
+++ b/aws-aggregator/requirements.txt
@@ -45,7 +45,7 @@ more-itertools==4.2.0
 mpld3==0.3
 nbconvert==5.3.1
 nbformat==4.4.0
-nltk==3.3
+nltk==3.6.3
 notebook==5.5.0
 numexpr==2.6.5
 numpy==1.14.3