diff --git a/book/_config.yml b/book/_config.yml
index 38e782ab..e7169d0d 100644
--- a/book/_config.yml
+++ b/book/_config.yml
@@ -11,11 +11,8 @@ execute:
 
 parse:
   myst_enable_extensions:
-    - substitution
     - linkify
     - dollarmath
-  myst_substitutions:
-    book_url: https://www.cvxgrp.org/cvxmarkowitz
 
 # needed for plotly
 sphinx: