Index: src/wp-includes/functions.php
===================================================================
--- src/wp-includes/functions.php	(revision 46647)
+++ src/wp-includes/functions.php	(working copy)
@@ -1946,7 +1946,7 @@
 	 * We also sometimes obey UPLOADS when rewriting is enabled -- see the next block.
 	 */
 	if ( defined( 'UPLOADS' ) && ! ( is_multisite() && get_site_option( 'ms_files_rewriting' ) ) ) {
-		$dir = ABSPATH . UPLOADS;
+		$dir = path_join( ABSPATH , UPLOADS );
 		$url = trailingslashit( $siteurl ) . UPLOADS;
 	}