diff --git a/src/edit.c b/src/edit.c
index 73ed472..0ba2627 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -2770,7 +2770,7 @@
  * 'completeopt' value.
  */
     void
-completeopt_was_set()
+completeopt_was_set(void)
 {
     compl_no_insert = FALSE;
     compl_no_select = FALSE;