diff --git a/sys/kern/uipc_sockbuf.c b/sys/kern/uipc_sockbuf.c
index e76f198f42d..406fdca11b4 100644
--- a/sys/kern/uipc_sockbuf.c
+++ b/sys/kern/uipc_sockbuf.c
@@ -1328,7 +1328,8 @@ sbappendcontrol_locked(struct sockbuf *sb, struct mbuf *m0,
 {
 	struct mbuf *m, *mlast;
 
-	kmsan_check_mbuf(m0, "sbappend");
+	if (m0 != NULL)
+		kmsan_check_mbuf(m0, "sbappend");
 	kmsan_check_mbuf(control, "sbappend");
 
 	sbm_clrprotoflags(m0, flags);