diff --git a/requirement.txt b/requirement.txt
index fa044a1..48e21f4 100644
--- a/requirement.txt
+++ b/requirement.txt
@@ -27,7 +27,7 @@ mistune==0.8.4
 mpmath==1.1.0
 nbconvert==5.4.0
 nbformat==4.4.0
-nltk==3.3
+nltk==3.4.5
 notebook>=5.7.8
 numpy==1.12.1
 packaging==16.8