Index: wp-includes/js/autosave.js
===================================================================
--- wp-includes/js/autosave.js	(revision 24718)
+++ wp-includes/js/autosave.js	(working copy)
@@ -242,7 +242,7 @@
 
 function autosave_enable_buttons() {
 	jQuery(document).trigger('autosave-enable-buttons');
-	if ( ! wp.heartbeat.connectionLost ) {
+	if ( wp.heartbeat.hasActiveConnection() ) {
 		// delay that a bit to avoid some rare collisions while the DOM is being updated.
 		setTimeout(function(){
 			var parent = jQuery('#submitpost');