diff --git a/static/js/variant.js b/static/js/variant.js
index c8812c9575..d79794ad46 100644
--- a/static/js/variant.js
+++ b/static/js/variant.js
@@ -361,7 +361,7 @@ var variants = {
 		}
 		if( !read_style ){
 			if( with_prompt ){
-				alert( 'A auto mode variant can not be changed. Please select its light/dark variant directly to make changes' );
+				alert( 'An auto mode variant can not be changed. Please select its light/dark variant directly to make changes' );
 			}
 			return;
 		}
@@ -426,6 +426,10 @@ var variants = {
 		if( !read_style ){
 			read_style = write_style;
 		}
+		if( !read_style ){
+			alert( 'An auto mode variant will be generated by Hugo and must not be stored in a separate stylesheet' );
+			return;
+		}
 
 		var style =
 			'/* ' + this.customvariantname + ' */\n' +