diff --git a/src/optionstr.c b/src/optionstr.c
index d667e53..e82654a 100644
--- a/src/optionstr.c
+++ b/src/optionstr.c
@@ -3565,7 +3565,7 @@
  * Process the new 'tabpanelopt' option value.
  */
     char *
-did_set_tabpanelopt(optset_T *args)
+did_set_tabpanelopt(optset_T *args UNUSED)
 {
     if (tabpanelopt_changed() == FAIL)
 	return e_invalid_argument;