diff --git a/episodes/04-docker-for-mc-generators-rivet.md b/episodes/04-docker-for-mc-generators-rivet.md
index 2335059..bcf4c60 100644
--- a/episodes/04-docker-for-mc-generators-rivet.md
+++ b/episodes/04-docker-for-mc-generators-rivet.md
@@ -140,7 +140,7 @@ cat output.txt
 :::::::::::::::::::::::::
 :::::::::::::::::::::::::::::::::::::::::::::::
 
-
+::::::::::::::::::::::::::::::::::::: challenge
 
 ### Challenge 3