Index: wp-includes/functions.php
===================================================================
--- wp-includes/functions.php	(revision 10216)
+++ wp-includes/functions.php	(working copy)
@@ -2804,7 +2804,15 @@
  * @return bool True if SSL, false if not used.
  */
 function is_ssl() {
-	return ( isset($_SERVER['HTTPS']) && 'on' == strtolower($_SERVER['HTTPS']) ) ? true : false;
+	if ( isset($_SERVER['HTTPS']) ) {
+		if ( 'on' == strtolower($_SERVER['HTTPS']) )
+			return true;
+		if ( '1' == $_SERVER['HTTPS'] )
+			return true;
+	} elseif ( isset($_SERVER['SERVER_PORT']) && ( '443' == $_SERVER['SERVER_PORT'] ) ) {
+		return true;
+	}
+	return false;
 }
 
 /**