diff --git a/src/Ftp/FtpAdapter.php b/src/Ftp/FtpAdapter.php
index 53386374e..12a2c7d37 100644
--- a/src/Ftp/FtpAdapter.php
+++ b/src/Ftp/FtpAdapter.php
@@ -634,6 +634,9 @@ private function hasFtpConnection(): bool
         return $this->connection instanceof \FTP\Connection || is_resource($this->connection);
     }
 
+    /**
+     * @param resource|\FTP\Connection$connection
+     */
     private function resolveConnectionRoot($connection): string
     {
         $root = $this->connectionOptions->root();