diff --git a/src/Gaufrette/Adapter/PhpseclibSftp.php b/src/Gaufrette/Adapter/PhpseclibSftp.php
index f4202d1f..befa1924 100644
--- a/src/Gaufrette/Adapter/PhpseclibSftp.php
+++ b/src/Gaufrette/Adapter/PhpseclibSftp.php
@@ -180,7 +180,7 @@ protected function initialize(): void
         $this->initialized = true;
     }
 
-    protected function ensureDirectoryExists(string $directory, bool $create)
+    protected function ensureDirectoryExists(string $directory, bool $create): void
     {
         $pwd = $this->sftp->pwd();
         if ($this->sftp->chdir($directory)) {