dm_coa_Class_change

diff --git a/accel-pppd/radius/dm_coa.c b/accel-pppd/radius/dm_coa.c
index ea9743d..2393d53 100644
--- a/accel-pppd/radius/dm_coa.c
+++ b/accel-pppd/radius/dm_coa.c
@@ -179,7 +179,7 @@ static void coa_request(struct radius_pd_t *rpd)
 			if (prev_class)
 				rad_packet_change_octets(rpd->acct_req->pack, NULL, "Class", rpd->attr_class, rpd->attr_class_len);
 			else
-				rad_packet_add_octets(rpd->acct_req->pack, NULL, "Class", rpd->attr_class, rpd->attr_class_len);
+				rad_packet_change_octets(rpd->acct_req->pack, NULL, "Class", rpd->attr_class, rpd->attr_class_len);
 		}
 
 		attr = rad_packet_find_attr(rpd->dm_coa_req, NULL, "Session-Timeout");