diff --git a/sys/sys/soundcard.h b/sys/sys/soundcard.h
index 7cf1f8b65590..4396b4fe5521 100644
--- a/sys/sys/soundcard.h
+++ b/sys/sys/soundcard.h
@@ -1095,7 +1095,7 @@ typedef struct copr_msg {
  */
 
 #ifndef USE_SIMPLE_MACROS
-void seqbuf_dump(void);	/* This function must be provided by programs */
+void seqbuf_dump __P((void));	/* This function must be provided by programs */
 
 /* Sample seqbuf_dump() implementation:
  *