diff --git a/books/thoughtful_ml/requirements.txt b/books/thoughtful_ml/requirements.txt
old mode 100755
new mode 100644
index 3d11e0a..325ce55
--- a/books/thoughtful_ml/requirements.txt
+++ b/books/thoughtful_ml/requirements.txt
@@ -20,7 +20,7 @@ jupyter-core==4.4.0
 kiwisolver==1.0.1
 MarkupSafe==1.0
 matplotlib==2.2.3
-mistune==0.8.3
+mistune==2.0.3
 nbconvert==5.4.0
 nbformat==4.4.0
 nose==1.3.7