diff --git a/books/thoughtful_ml/requirements.txt b/books/thoughtful_ml/requirements.txt
old mode 100755
new mode 100644
index 3d11e0a..1ddacf2
--- a/books/thoughtful_ml/requirements.txt
+++ b/books/thoughtful_ml/requirements.txt
@@ -21,7 +21,7 @@ kiwisolver==1.0.1
 MarkupSafe==1.0
 matplotlib==2.2.3
 mistune==0.8.3
-nbconvert==5.4.0
+nbconvert==6.5.1
 nbformat==4.4.0
 nose==1.3.7
 notebook==5.7.8