diff --git a/wp-includes/js/customize-preview.js b/wp-includes/js/customize-preview.js
index 9caa6b684a..caefe653a9 100644
--- a/wp-includes/js/customize-preview.js
+++ b/wp-includes/js/customize-preview.js
@@ -129,7 +129,7 @@
 					css += 'background-image: url("' + image() + '");';
 					css += 'background-position: top ' + position_x() + ';';
 					css += 'background-repeat: ' + repeat() + ';';
-					css += 'background-position: top ' + attachment() + ';';
+					css += 'background-attachment: ' + attachment() + ';';
 				}
 
 				// Refresh the stylesheet by removing and recreating it.