diff --git a/js/jquery.mobile.popup.js b/js/jquery.mobile.popup.js
index 6e52d954..57c21537 100644
--- a/js/jquery.mobile.popup.js
+++ b/js/jquery.mobile.popup.js
@@ -139,9 +139,9 @@ $.widget("mobile.popup", $.mobile.widget, {
 		var ret,
 		    menuHeight = this._ui.container.outerHeight(true),
 		    menuWidth = this._ui.container.outerWidth(true),
-		    scrollTop = $( window ).scrollTop(),
-		    screenHeight = window.innerHeight,
-		    screenWidth = window.innerWidth,
+		    scrollTop = $(window).scrollTop(),
+		    screenHeight = $(window).height(),
+		    screenWidth = $(window).width(),
 		    halfheight = menuHeight / 2,
 		    maxwidth = parseFloat( this._ui.container.css( "max-width" ) ),
 		    roomtop = y - scrollTop,