diff --git a/src/wp-admin/js/customize-controls.js b/src/wp-admin/js/customize-controls.js
index 8cc4130245..9c28a96d5f 100644
--- a/src/wp-admin/js/customize-controls.js
+++ b/src/wp-admin/js/customize-controls.js
@@ -482,6 +482,7 @@
 
 			data.url = url;
 			data.thumbnail_url = url;
+			data.timestamp = _.now();
 
 			if (attachmentId) {
 				data.attachment_id = attachmentId;