diff --git a/src/Exportable.php b/src/Exportable.php
index f309bc4..e933a6d 100644
--- a/src/Exportable.php
+++ b/src/Exportable.php
@@ -36,6 +36,7 @@ abstract protected function setOptions(&$options);
     /**
      * @param string        $path
      * @param callable|null $callback
+     * @param string        $ext
      *
      * @throws \OpenSpout\Common\Exception\InvalidArgumentException
      * @throws \OpenSpout\Common\Exception\UnsupportedTypeException
@@ -54,6 +55,7 @@ public function export($path, callable $callback = null, $ext = null)
     /**
      * @param               $path
      * @param callable|null $callback
+     * @param string        $ext
      *
      * @throws \OpenSpout\Common\Exception\InvalidArgumentException
      * @throws \OpenSpout\Common\Exception\UnsupportedTypeException