diff --git a/ui/jquery.ui.core.js b/ui/jquery.ui.core.js
index 51f6b71d7..8bcc4c441 100644
--- a/ui/jquery.ui.core.js
+++ b/ui/jquery.ui.core.js
@@ -174,6 +174,27 @@ $.each( [ "Width", "Height" ], function( i, name ) {
 });
 
 // selectors
+function focusable( element, isTabIndexNotNaN ) {
+	var nodeName = element.nodeName.toLowerCase();
+	if ( "area" === nodeName ) {
+		var map = element.parentNode,
+			mapName = map.name,
+			img;
+		if ( !element.href || !mapName || map.nodeName.toLowerCase() !== "map" ) {
+			return false;
+		}
+		img = $( "img[usemap=#" + mapName + "]" )[0];
+		return !!img && visible( img );
+	}
+	return ( /input|select|textarea|button|object/.test( nodeName )
+		? !element.disabled
+		: "a" == nodeName
+			? element.href || isTabIndexNotNaN
+			: isTabIndexNotNaN)
+		// the element and all of its ancestors must be visible
+		&& visible( element );
+}
+
 function visible( element ) {
 	return !$( element ).parents().andSelf().filter(function() {
 		return $.curCSS( this, "visibility" ) === "hidden" ||
@@ -187,30 +208,13 @@ $.extend( $.expr[ ":" ], {
 	},
 
 	focusable: function( element ) {
-		var nodeName = element.nodeName.toLowerCase(),
-			tabIndex = $.attr( element, "tabindex" );
-		if ( "area" === nodeName ) {
-			var map = element.parentNode,
-				mapName = map.name,
-				img;
-			if ( !element.href || !mapName || map.nodeName.toLowerCase() !== "map" ) {
-				return false;
-			}
-			img = $( "img[usemap=#" + mapName + "]" )[0];
-			return !!img && visible( img );
-		}
-		return ( /input|select|textarea|button|object/.test( nodeName )
-			? !element.disabled
-			: "a" == nodeName
-				? element.href || !isNaN( tabIndex )
-				: !isNaN( tabIndex ))
-			// the element and all of its ancestors must be visible
-			&& visible( element );
+		return focusable( element, !isNaN( $.attr( element, "tabindex" ) ) );
 	},
 
 	tabbable: function( element ) {
-		var tabIndex = $.attr( element, "tabindex" );
-		return ( isNaN( tabIndex ) || tabIndex >= 0 ) && $( element ).is( ":focusable" );
+		var tabIndex = $.attr( element, "tabindex" ),
+			isTabIndexNaN = isNaN( tabIndex );
+		return ( isTabIndexNaN || tabIndex >= 0 ) && focusable( element, !isTabIndexNaN );
 	}
 });