[exim] router_home_directory isn't work?

Hello.

the router:
userdb_forward:
  driver                = redirect
  domains               = +local_domains
  address_data          = GET_ADDRESS_DATA
  check_local_user      = false
  no_verify
  allow_filter
  filter_prepend_home   = true
  user                  = ${extract{uid}{$address_data}}
  no_expn
  check_ancestor
  file                  = ${extract{home}{$address_data}}/.forward
  router_home_directory = ${extract{home}{$address_data}}/
  directory_transport   = address_directory
  pipe_transport        = address_pipe
  reply_transport       = address_reply

were .forward is:
# Exim filter
save Maildir/

exim -d -bt :
....................
userdb_forward router generated //Maildir/
pipe, file, or autoreply
errors_to=NULL transport=address_directory

routed by userdb_forward router
envelope to: test@???
transport: <none>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Considering //Maildir/
test@??? -> //Maildir/
transport = address_directory

if I change router_home_directory =
/xxx/${extract{home}{$address_data}}/xxx/ then i have:

exim -d -bt :
..................
userdb_forward router generated /xxx//xxx//Maildir/
pipe, file, or autoreply
errors_to=NULL transport=address_directory
uid=zzzzz gid=zzzzz home=/xxx//xxx/
routed by userdb_forward router
envelope to: test@???
transport: <none>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Considering /xxx//xxx//Maildir/
test@??? -> /xxx//xxx//Maildir/

I don't no why ${exctract dosen't work in "router_home_directory". In
"file" it work fine.
exim-4.64-4