diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c
index e3d857d2d2c..cadfd623930 100644
--- a/sys/kern/kern_prot.c
+++ b/sys/kern/kern_prot.c
@@ -1862,6 +1862,8 @@ setlogin(struct thread *td, struct setlogin_args *uap)
 void
 setsugid(struct proc *p)
 {
+
+	PROC_LOCK_ASSERT(p, MA_OWNED);
 	p->p_flag |= P_SUGID;
 	if (!(p->p_pfsflags & PF_ISUGID))
 		p->p_stops = 0;