diff --git a/stepmania/NoteSkins/common/common/NoteSkin.lua b/stepmania/NoteSkins/common/common/NoteSkin.lua
index 74115e7a97..ebf6f2d9a5 100644
--- a/stepmania/NoteSkins/common/common/NoteSkin.lua
+++ b/stepmania/NoteSkins/common/common/NoteSkin.lua
@@ -37,6 +37,8 @@ local function func()
 	end
 
 	local sButtonToLoad, sElementToLoad = ret.Redir(sButton, sElement);
+	assert( sButtonToLoad );
+	assert( sElementToLoad );
 
 	local sPath = NOTESKIN:GetPath( sButtonToLoad, sElementToLoad );