diff --git a/Contrib/Modern UI/System.nsh b/Contrib/Modern UI/System.nsh
index fc46c89e..778051c1 100644
--- a/Contrib/Modern UI/System.nsh	
+++ b/Contrib/Modern UI/System.nsh	
@@ -960,7 +960,7 @@ Var MUI_TEMP2
 
   !ifdef MUI_PAGE_CUSTOMFUNCTION_${TYPE}
     Call "${MUI_PAGE_CUSTOMFUNCTION_${TYPE}}"
-    !undef "${MUI_PAGE_CUSTOMFUNCTION_${TYPE}}"
+    !undef MUI_PAGE_CUSTOMFUNCTION_${TYPE}
   !endif
   
 !macroend