[Users] avpops, duplicate key, empty username and domain

Hi, I'm trying to use avpops module, but I'm facing the following error: 0(8178) PG[367] submit_query query 'insert into usr_preferences (uuid,attribute,value,type,username,domain ) values ('test','avpname','test',0,'','')', result 'ERROR: duplicate key violates unique constraint "usr_preferences_pkey" It seems to be caused by the username and domain parameters being empty strings, since the usr_preferences table has this PK constraint: "usr_preferences_pkey" primary key, btree (attribute, username, "domain") The avpops module is configured like this: modparam("avpops", "avp_url", "postgres://xpto:xpto@127.0.0.1/xpto") modparam("avpops", "avp_table", "usr_preferences") modparam("avpops","use_domain",1) modparam("avpops", "avp_aliases", "avpalias=s:avpname") And I'm simply doing: avp_printf("s:avpname", "test"); avp_db_store("$avpalias/uuid", "s:avpname"); What may be missing? Maybe the usr_preferences table should not have this PK when using UUID-based AVP identification... JF