Index: ms-functions.php
===================================================================
--- ms-functions.php	(revision 18542)
+++ ms-functions.php	(working copy)
@@ -384,7 +384,7 @@
 
 	if ( !$id ) {
 		wp_cache_set( md5( $domain . $path ), -1, 'blog-id-cache' );
-		return false;
+		return 0;
 	}
 	wp_cache_set( md5( $domain . $path ), $id, 'blog-id-cache' );