diff --git a/src/clipboard.c b/src/clipboard.c
index b09c678..4ce536a 100644
--- a/src/clipboard.c
+++ b/src/clipboard.c
@@ -257,7 +257,7 @@
  * right text.
  */
     static int
-is_clipboard_needs_update()
+is_clipboard_needs_update(void)
 {
     return clipboard_needs_update;
 }