diff --git a/grub-core/commands/parttool.c b/grub-core/commands/parttool.c
index d907694dd..42c590e1a 100644
--- a/grub-core/commands/parttool.c
+++ b/grub-core/commands/parttool.c
@@ -282,8 +282,11 @@ grub_cmd_parttool (grub_command_t cmd __attribute__ ((unused)),
 		break;
 	    }
 	if (! cur)
-	  return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("unknown argument `%s'"),
+	  {
+	    grub_device_close (dev);
+	    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("unknown argument `%s'"),
 			     args[i]);
+	  }
 	ptool = cur;
 	pargs = (struct grub_parttool_args *)
 	  grub_zalloc (ptool->nargs * sizeof (struct grub_parttool_args));