EXIM - send message copy with big spam_score

Question

I'm trying to setup mail relay.

I want to send message copy with spam_score greater than SPAM_SCORE_THRESHOLD.

But the rule is not working, and it send copies even with spam_score lower than SPAM_SCORE_THRESHOLD.

What is wrong with my config?

ROUTER_SPAM_FILTER =
SPAM_SCORE_THRESHOLD = 300
...
warn   hosts      = ! +relay_from_hosts  
       spam       = nobody/defer_ok 
       add_header = X-Spam-Flag: YES 
       logwrite   = SPAM_SCORE: $sender_address $spam_score_int 
       set acl_m2 = $spam_score_int 
...
.ifdef ROUTER_SPAM_FILTER  
 spam_filter:                 
  condition = ${if >{$acl_m2}{$SPAM_SCORE_THRESHOLD}{true}}
  unseen
  driver = redirect
  data = spam@aggregator.domain.com
.endif