diff --git a/examples/CH_11/requirements.txt b/examples/CH_11/requirements.txt
old mode 100755
new mode 100644
index 81569f4..91342a1
--- a/examples/CH_11/requirements.txt
+++ b/examples/CH_11/requirements.txt
@@ -34,7 +34,7 @@ pbr==5.8.1
 premailer==3.10.0
 pycodestyle==2.8.0
 pycparser==2.21
-Pygments==2.11.2
+Pygments==2.15.0
 pyjwt==2.4.0
 python-dateutil==2.8.2
 python-editor==1.0.4