diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index e0a392d..e6ef381 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -1174,7 +1174,7 @@
  * Return the time in msec until the next timer is due.
  */
     long
-check_due_timer()
+check_due_timer(void)
 {
     timer_T	*timer;
     long	this_due;