Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 20767)
+++ wp-includes/post.php	(working copy)
@@ -3823,6 +3823,12 @@
 	$backup_sizes = get_post_meta( $post->ID, '_wp_attachment_backup_sizes', true );
 	$file = get_attached_file( $post_id );
 
+	$intermediate_sizes = array();
+	foreach ( get_intermediate_image_sizes() as $size ) {
+		if ( $intermediate = image_get_intermediate_size( $post_id, $size ) )
+			$intermediate_sizes[] = $intermediate;
+	}
+
 	if ( is_multisite() )
 		delete_transient( 'dirsize_cache' );
 
@@ -3857,11 +3863,9 @@
 	}
 
 	// remove intermediate and backup images if there are any
-	foreach ( get_intermediate_image_sizes() as $size ) {
-		if ( $intermediate = image_get_intermediate_size($post_id, $size) ) {
-			$intermediate_file = apply_filters('wp_delete_file', $intermediate['path']);
-			@ unlink( path_join($uploadpath['basedir'], $intermediate_file) );
-		}
+	foreach ( $intermediate_sizes as $intermediate ) {
+		$intermediate_file = apply_filters( 'wp_delete_file', $intermediate['path'] );
+		@ unlink( path_join($uploadpath['basedir'], $intermediate_file) );
 	}
 
 	if ( is_array($backup_sizes) ) {