diff --git a/lib/privs.c b/lib/privs.c
index 14f0090197..2932800070 100644
--- a/lib/privs.c
+++ b/lib/privs.c
@@ -799,7 +799,7 @@ void zprivs_init(struct zebra_privs_t *zprivs)
 		return;
 
 	if (zprivs->user) {
-		ngroups = sizeof(groups);
+		ngroups = array_size(groups);
 		if (getgrouplist(zprivs->user, zprivs_state.zgid, groups,
 				 &ngroups)
 		    < 0) {