diff --git src/wp-admin/js/customize-controls.js src/wp-admin/js/customize-controls.js
index 90b8411..99320bc 100644
--- src/wp-admin/js/customize-controls.js
+++ src/wp-admin/js/customize-controls.js
@@ -4173,7 +4173,7 @@
 				_.find( parsedCandidateUrls, function( parsedCandidateUrl ) {
 					return ! _.isUndefined( _.find( previewer.allowedUrls, function( allowedUrl ) {
 						parsedAllowedUrl.href = allowedUrl;
-						if ( urlParser.protocol === parsedAllowedUrl.protocol && urlParser.host === parsedAllowedUrl.host && 0 === parsedAllowedUrl.pathname.indexOf( urlParser.pathname ) ) {
+						if ( urlParser.protocol === parsedAllowedUrl.protocol && urlParser.host === parsedAllowedUrl.host && 0 === urlParser.pathname.indexOf( parsedAllowedUrl.pathname ) ) {
 							result = parsedCandidateUrl.href;
 							return true;
 						}