modheader chrome extension with privoxy

Hello,

I'm trying to use modheader extension behind Privoxy.

I suspect it's blocked by the proxy but I can't figure how to allow it
to work using the config files.

error msg : ERR_BLOCKED_BY_CLIENT


First, I tried to put the destination server in the' fragile' section of
user.action but it does nothing.

any idea ?

thanks for the reading.