diff --git src/wp-includes/js/quicktags.js src/wp-includes/js/quicktags.js
index 9fc9c69..c820ff4 100644
--- src/wp-includes/js/quicktags.js
+++ src/wp-includes/js/quicktags.js
@@ -230,14 +230,18 @@ function edButton(id, display, tagStart, tagEnd, access) {
 
 		qt.instances[id] = t;
 
-		if ( !qt.instances[0] ) {
-			qt.instances[0] = qt.instances[id];
+		if ( qt.instances[id] ) {
 			_domReady( function(){ qt._buttonsInit(); } );
 		}
 	};
 
 	qt.instances = {};
 
+	qt.addInstance = function(settings) {
+		if( 'id' in settings )
+			return qt.instances[settings.id] = settings;
+	};
+
 	qt.getInstance = function(id) {
 		return qt.instances[id];
 	};