sagepay - ReferrerId too short -

referrerid on sagepay documentation definited not mandatory, receive error 'referrer id short'. tried pass null or valorized vendor name received same error in both cases.

anyone knows why , how resolve problem? using prolcol 3.00 , error on sagepay test environment.

remove string completely. if field submitted sage pay try validate it's contents , return error if doesn't meet requirements. referrerid used validate sage pay partner has referred sage pay user.