diff --git a/src/keyboard.c b/src/keyboard.c
index 8128eaca2d9..48627162ff5 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -3299,7 +3299,7 @@ kbd_buffer_store_event (event)
 
       if (c == quit_char)
 	{
-	  static SIGTYPE interrupt_signal (int);
+	  static SIGTYPE interrupt_signal P_ ((int));
 #ifdef MULTI_KBOARD
 	  KBOARD *kb;
 	  struct input_event *sp;