Index: wp-includes/load.php
===================================================================
--- wp-includes/load.php	(revision 18316)
+++ wp-includes/load.php	(working copy)
@@ -639,9 +639,15 @@
 	if ( defined( 'MULTISITE' ) )
 		return MULTISITE;
 
-	if ( defined( 'SUBDOMAIN_INSTALL' ) || defined( 'VHOST' ) || defined( 'SUNRISE' ) )
+	if ( defined('SUBDOMAIN_INSTALL') )
+		return SUBDOMAIN_INSTALL;
+
+	if ( defined('VHOST') && VHOST == 'yes' )
 		return true;
 
+	if ( defined( 'SUNRISE' ) )
+		return true;
+
 	return false;
 }