diff --git a/sys/kern/subr_witness.c b/sys/kern/subr_witness.c
index 02ba3a1481a2..140dafaeb74e 100644
--- a/sys/kern/subr_witness.c
+++ b/sys/kern/subr_witness.c
@@ -277,6 +277,7 @@ static struct witness_order_list_entry order_lists[] = {
 #ifdef __i386__
 	{ "cy", &lock_class_mtx_spin },
 #endif
+	{ "uart_hwmtx", &lock_class_mtx_spin },
 	{ "sabtty", &lock_class_mtx_spin },
 	{ "zstty", &lock_class_mtx_spin },
 	{ "ng_node", &lock_class_mtx_spin },