100% type coverage for psalm

src/Rclone/Rclone.php

@@ -14,7 +14,7 @@ use Exception;
  *
  * Installation of rclone is required.
  * Configuration of the mounts must be done before use.
- * Tested using rclone v1.53.3-DEV
+ * Tested using rclone v1.62.2
  */
 class Rclone
 {
@@ -97,7 +97,7 @@ class Rclone
         $options[] = $dest;
 
         foreach ($additionalOptions as $key => $value) {
-            $options[] = '--' . $key;
+            $options[] = '--' . (string)$key;
             $options[] = $value;
         }