diff --git a/requirements.txt b/requirements.txt
index 3c161b2..9faa730 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -33,7 +33,7 @@ mistune==0.7.4
 mongoengine==0.10.7
 nbconvert==5.3.1
 nbformat==4.4.0
-nltk==3.2.4
+nltk==3.4.5
 notebook==5.0.0
 numpy==1.13.1
 pandas==0.20.3