Index: wp-includes/js/autosave.dev.js
===================================================================
--- wp-includes/js/autosave.dev.js	(revision 17537)
+++ wp-includes/js/autosave.dev.js	(working copy)
@@ -161,8 +161,12 @@
 				samplepermalinknonce: jQuery('#samplepermalinknonce').val()
 			},
 			function(data) {
-				jQuery('#edit-slug-box').html(data);
-				makeSlugeditClickable();
+				if ( data === '-1' ) {
+					jQuery('#edit-slug-box').html('');
+				} else {
+					jQuery('#edit-slug-box').html(data);
+					makeSlugeditClickable();
+				}
 			}
 		);
 	}