diff --git a/Changing-the-Battle-Music-Depending-on-the-Opponent.md b/Changing-the-Battle-Music-Depending-on-the-Opponent.md
index 84f273c..b681311 100644
--- a/Changing-the-Battle-Music-Depending-on-the-Opponent.md
+++ b/Changing-the-Battle-Music-Depending-on-the-Opponent.md
@@ -4,7 +4,9 @@ For this tutorial, I'm going to replace Sidney of the Elite Four's battle with t
 
 Open src/pokemon.c.
 
-Search for `u16 GetBattleBGM(void)`.
+Underneath the last `#include`, add `#include "constants/opponents.h"` on a new line. THIS IS IMPORTANT! DON'T FORGET TO ADD THIS OTHERWISE YOUR COMPILER WILL THROW AN ERROR!
+
+Next, search for `u16 GetBattleBGM(void)`.
 
 In the `switch (trainerClass)` statement, add a statement like this:
 ```diff