diff --git a/handson-ml-master/requirements.txt b/handson-ml-master/requirements.txt
index 163ce62..64eb88a 100644
--- a/handson-ml-master/requirements.txt
+++ b/handson-ml-master/requirements.txt
@@ -74,7 +74,7 @@ numexpr==2.6.9
 
 # Optional: these libraries can be useful in the classification chapter,
 # exercise 4.
-nltk==3.4.5
+nltk==3.6.6
 urlextract==0.9
 
 # Optional: tqdm displays nice progress bars, ipywidgets for tqdm's notebook support