Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 13283)
+++ wp-includes/post.php	(working copy)
@@ -2392,7 +2392,7 @@
 		$check_sql = "SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND post_type IN ( '" . implode( "', '", esc_sql( $hierarchical_post_types ) ) . "' ) AND ID != %d AND post_parent = %d LIMIT 1";
 		$post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, $slug, $post_ID, $post_parent ) );
 
-		if ( $post_name_check || in_array( $slug, $feeds ) ) {
+		if ( $post_name_check || in_array( $slug, $feeds ) || 1 === preg_match('@^\d+$@', $slug) ) {
 			$suffix = 2;
 			do {
 				$alt_post_name = substr( $slug, 0, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";