diff --git a/book/_toc.yml b/book/_toc.yml
index c4ab36323cf24fe770c3da44d35d0a07f8f79d5f..220d66c1b8e213004d3864d616ba7f945e7b3c6d 100644
--- a/book/_toc.yml
+++ b/book/_toc.yml
@@ -396,6 +396,7 @@ parts:
       sections:
       - file: external/learn-python/book/08/sympy
     - file: optimization/gurobi.md
+      sections:
       title: Gurobi
 
     # THIS IS FOR WEEK 2.5