diff --git a/books/zero_to_deep_learning/requirements.txt b/books/zero_to_deep_learning/requirements.txt
old mode 100755
new mode 100644
index b5ad23a..e752797
--- a/books/zero_to_deep_learning/requirements.txt
+++ b/books/zero_to_deep_learning/requirements.txt
@@ -31,7 +31,7 @@ Keras==2.2.0
 Keras-Applications==1.0.2
 Keras-Preprocessing==1.0.1
 kiwisolver==1.0.1
-lxml==4.2.3
+lxml==4.9.1
 Markdown==2.6.11
 MarkupSafe==1.0
 matplotlib==2.2.2