Index: wp-includes/js/heartbeat.js
===================================================================
--- wp-includes/js/heartbeat.js	(revision 31863)
+++ wp-includes/js/heartbeat.js	(working copy)
@@ -342,7 +342,7 @@
 		 * @return void
 		 */
 		function connect() {
-			var ajaxData, heartbeatData;
+			var ajaxData, heartbeatData, heartbeatURL;
 
 			// If the connection to the server is slower than the interval,
 			// heartbeat connects as soon as the previous connection's response is received.
@@ -356,6 +356,13 @@
 			// Clear the data queue, anything added after this point will be send on the next tick
 			settings.queue = {};
 
+			// Set a query variable to AJAX URL to allow differentiating Heartbeat requests.
+			if ( settings.url.indexOf( '?' ) === -1 ) {
+				heartbeatURL = settings.url + '?heartbeat=1';
+			} else {
+				heartbeatURL = settings.url + '&heartbeat=1';
+			}
+
 			$document.trigger( 'heartbeat-send', [ heartbeatData ] );
 
 			ajaxData = {
@@ -369,7 +376,7 @@
 
 			settings.connecting = true;
 			settings.xhr = $.ajax({
-				url: settings.url,
+				url: heartbeatURL,
 				type: 'post',
 				timeout: 30000, // throw an error if not completed after 30 sec.
 				data: ajaxData,