diff --git a/book/_toc.yml b/book/_toc.yml
index f5bee08..5e39197 100644
--- a/book/_toc.yml
+++ b/book/_toc.yml
@@ -73,7 +73,7 @@ parts:
         title: "Practice: The Sudden Approximation in 2-D"
       - url: https://classroom.github.com/a/TSS2Sbin
         title: "Practice: Interacting particles in a box"
-      - url: https://classroom.github.com/a/8wy0Ss-1
+      - url: https://classroom.github.com/a/gHbKRyrp
         title: "Quiz: MultiD P-in-Box"
 
     - file: Postulates.ipynb