diff --git a/Ch4/ch4-requirements.txt b/Ch4/ch4-requirements.txt
index ae20396..de12cf8 100644
--- a/Ch4/ch4-requirements.txt
+++ b/Ch4/ch4-requirements.txt
@@ -1,7 +1,7 @@
 numpy==1.19.5
 pandas==1.1.5
 scikit-learn==0.23.2
-nltk==3.5
+nltk==3.6.6
 gensim==3.8.3
 wget==3.2
 fasttext==0.9.2