diff --git a/ui/jquery.ui.dialog.js b/ui/jquery.ui.dialog.js
index 932f392951..ae96b2d8b9 100644
--- a/ui/jquery.ui.dialog.js
+++ b/ui/jquery.ui.dialog.js
@@ -706,7 +706,11 @@ $.extend($.ui.dialog.overlay, {
 		}
 
 		var $el = (this.oldInstances.pop() || $('<div></div>').addClass('ui-widget-overlay'))
-			.appendTo(document.body);
+			.appendTo(document.body)
+			.css({
+				width: this.width(),
+				height: this.height()
+			});
 
 		if ($.fn.bgiframe) {
 			$el.bgiframe();