[exim] Content-Scanning $spam_score_int

Hello,

what could be the reason that $spam_score is set but $spam_score_int isn't?

acl_check_data:
***************
  warn    message   = X-Spam-Score: $spam_score ($spam_bar)
          spam      = nobody:true
  warn    message   = X-Spam-Report: $spam_report
          spam      = nobody:true

  deny    message   = Classified as spam (score 
$spam_score)\nX-Spam-Report:$spam_report
          condition = ${if >{$spam_score_int}{400}{1}{0}}
          spam      = nobody:true/defer_ok
***************

Debug:
******
[...]
1873 check spam = nobody:true
1873 warn: condition test succeeded
1873 processing "deny"
1873 check condition = ${if >{$spam_score_int}{400}{1}{0}}
1873                 = 0
1873 deny: condition test failed
1873 processing "accept"
1873 accept: condition test succeeded
1873 >>Headers added by DATA ACL:
1873   X-Spam-Score: 10.3 (++++++++++)
[...]
******

Cheers,
christian