diff --git a/hands-on-ml-with-sklearn-and-tf/handson-ml-master/requirements.txt b/hands-on-ml-with-sklearn-and-tf/handson-ml-master/requirements.txt
index 69bf446..69b61f3 100644
--- a/hands-on-ml-with-sklearn-and-tf/handson-ml-master/requirements.txt
+++ b/hands-on-ml-with-sklearn-and-tf/handson-ml-master/requirements.txt
@@ -80,7 +80,7 @@ numexpr==2.6.5
 
 # Optional: these libraries can be useful in the classification chapter,
 # exercise 4.
-nltk==3.3
+nltk==3.6.3
 urlextract==0.8.3
 
 # Optional: this extension is handy to easily start/stop tensorboard