diff --git a/src/eval.c b/src/eval.c
index 2f370b7..aab9b0b 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -16664,7 +16664,7 @@
  */
     static void
 f_shiftwidth(argvars, rettv)
-    typval_T	*argvars;
+    typval_T	*argvars UNUSED;
     typval_T	*rettv;
 {
     rettv->vval.v_number = get_sw_value();