diff --git a/ui/jquery.ui.tooltip.js b/ui/jquery.ui.tooltip.js
index 924ce4121..cb23e9a4d 100644
--- a/ui/jquery.ui.tooltip.js
+++ b/ui/jquery.ui.tooltip.js
@@ -103,7 +103,13 @@ $.widget( "ui.tooltip", {
 			target.data( "tooltip-title", target.attr( "title" ) );
 		}
 
+		target.data( "tooltip-open", true );
+
 		content = this.options.content.call( target[0], function( response ) {
+			// ignore async response if tooltip was closed already
+			if ( !target.data( "tooltip-open" ) ) {
+				return;
+			}
 			// IE may instantly serve a cached response for ajax requests
 			// delay this call to _open so the other call to _open runs first
 			setTimeout(function() {
@@ -186,6 +192,7 @@ $.widget( "ui.tooltip", {
 			delete that.tooltips[ this.id ];
 		});
 
+		target.removeData( "tooltip-open" );
 		target.unbind( "mouseleave.tooltip blur.tooltip keyup.tooltip" );
 
 		this._trigger( "close", event, { tooltip: tooltip } );