diff --git a/examples/clustering_users/clustering_requirements.txt b/examples/clustering_users/clustering_requirements.txt
index fc4304d..5bd7fa4 100644
--- a/examples/clustering_users/clustering_requirements.txt
+++ b/examples/clustering_users/clustering_requirements.txt
@@ -30,7 +30,7 @@ mistune==0.8
 -e git+git://github.com/DmitryUlyanov/Multicore-TSNE#egg=Multicore-TSNE
 nbconvert==5.3.1
 nbformat==4.4.0
-nltk==3.2.5
+nltk==3.6.3
 notebook==5.2.0
 pandas==0.21.0
 pandocfilters==1.4.2