How remove SipHeader before call transfer?

I make originate between local extension to outside call. the originate call first to local extension with autoanswer by:

exten => _.,1,Set(__SIPADDHEADER=Call-Info: answer-after=0)
exten => _.,n,Set(__SIP_URI_OPTIONS=intercom=true)
exten => _.,n,Set(__ALERT_INFO=Ring Answer)

But when extension transfer this call, it’s make autoanswer to the Transfered extension.

So how I can set clear this var before Transfer take place?