Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 17643)
+++ wp-includes/post.php	(working copy)
@@ -2796,7 +2796,7 @@
 	} elseif ( in_array( $post_type, $hierarchical_post_types ) ) {
 		// Page slugs must be unique within their own trees. Pages are in a separate
 		// namespace than posts so page slugs are allowed to overlap post slugs.
-		$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";
+		$check_sql = "SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND post_type IN ( '" . implode( "', '", esc_sql( $hierarchical_post_types ) ) . "', 'attachment' ) 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, $feeds ) || preg_match( "@^($wp_rewrite->pagination_base)?\d+$@", $slug )  || apply_filters( 'wp_unique_post_slug_is_bad_hierarchical_slug', false, $slug, $post_type, $post_parent ) ) {
@@ -2810,7 +2810,7 @@
 		}
 	} else {
 		// Post slugs must be unique across all posts.
-		$check_sql = "SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND post_type = %s AND ID != %d LIMIT 1";
+		$check_sql = "SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND (post_type = %s OR post_type = 'attachment') AND ID != %d LIMIT 1";
 		$post_name_check = $wpdb->get_var( $wpdb->prepare( $check_sql, $slug, $post_type, $post_ID ) );
 
 		if ( $post_name_check || in_array( $slug, $feeds ) || apply_filters( 'wp_unique_post_slug_is_bad_flat_slug', false, $slug, $post_type ) ) {