Index: wp-includes/ms-functions.php
===================================================================
--- wp-includes/ms-functions.php	(revision 34219)
+++ wp-includes/ms-functions.php	(working copy)
@@ -1409,6 +1409,15 @@
 
 	$url = untrailingslashit( $url );
 
+	if ( defined( 'SUBDOMAIN_INSTALL' ) && SUBDOMAIN_INSTALL === false){
+ 		$siteurl = parse_url( get_site_option( 'siteurl' ) );
+
+		if ( $siteurl['scheme'] == 'https' ) {
+			$url = set_url_scheme( $url, 'https' );
+		}
+
+	}
+
 	update_option( 'siteurl', $url );
 	update_option( 'home', $url );