diff --git a/src/option.c b/src/option.c
index 85c3705..150e562 100644
--- a/src/option.c
+++ b/src/option.c
@@ -8847,7 +8847,7 @@
  * Process the new 'showtabpanel' option value.
  */
     char *
-did_set_showtabpanel(optset_T *args)
+did_set_showtabpanel(optset_T *args UNUSED)
 {
     shell_new_columns();
     return NULL;