diff --git a/sys/dev/disk/advansys/adwlib.c b/sys/dev/disk/advansys/adwlib.c
--- a/sys/dev/disk/advansys/adwlib.c
+++ b/sys/dev/disk/advansys/adwlib.c
@@ -826,6 +826,8 @@
 		if (mc_sdtr == adw_syncrates[i].mc_sdtr)
 			break;
 	}	
+	if (i >= adw_num_syncrates)
+		return (adw_syncrates[0].period);
 	return (adw_syncrates[i].period);
 }