diff --git a/wp-includes/post.php b/wp-includes/post.php
index b13942002a..7073328c0d 100644
--- a/wp-includes/post.php
+++ b/wp-includes/post.php
@@ -6162,7 +6162,7 @@ function wp_delete_attachment( $post_id, $force_delete = false ) {
 	$backup_sizes = get_post_meta( $post->ID, '_wp_attachment_backup_sizes', true );
 	$file         = get_attached_file( $post_id );
 
-	if ( is_multisite() ) {
+	if ( is_multisite() && is_string( $file ) && ! empty( $file ) ) {
 		clean_dirsize_cache( $file );
 	}
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 7c05884485..7c7da6bdf0 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51911';
+$wp_version = '5.9-alpha-51912';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.