Index: wp-includes/js/heartbeat.js
===================================================================
--- wp-includes/js/heartbeat.js	(revision 25069)
+++ wp-includes/js/heartbeat.js	(working copy)
@@ -427,7 +427,7 @@
 		 */
 		this.enqueue = function( handle, data, dont_overwrite ) {
 			if ( handle ) {
-				if ( queue.hasOwnProperty( handle ) && dont_overwrite )
+				if ( dont_overwrite && queue.hasOwnProperty( handle ) )
 					return false;
 
 				queue[handle] = data;
@@ -440,11 +440,23 @@
 		 * Check if data with a particular handle is queued
 		 *
 		 * $param string handle The handle for the data
-		 * $return mixed The data queued with that handle or null
+		 * $return mixed The data queued with that handle or undefined
 		 */
 		this.isQueued = function( handle ) {
-			return queue[handle];
+			if ( handle )
+				return queue[handle];
 		};
+
+		/**
+		 * Remove data with a particular handle from the queue
+		 *
+		 * $param string handle The handle for the data
+		 * $return void
+		 */
+		this.dequeue = function( handle ) {
+			if ( handle )
+				delete( queue[handle] );
+		};
 	};
 
 	$.extend( Heartbeat.prototype, {