diff --git a/usr.sbin/bluetooth/bthidd/kbd.c b/usr.sbin/bluetooth/bthidd/kbd.c
--- a/usr.sbin/bluetooth/bthidd/kbd.c
+++ b/usr.sbin/bluetooth/bthidd/kbd.c
@@ -339,7 +339,7 @@
 int32_t
 kbd_process_keys(bthid_session_p s)
 {
-	bitstr_t	diff[bitstr_size(xsize)];
+	bitstr_t	bit_decl(diff, xsize);
 	int32_t		f1, f2, i;
 
 	assert(s != NULL);