[exim] redirect router & headers_add

Hello,

I'm trying to set up redirecting infected messages to certain address.
I set up the data acl and `redirect' router:

acl_check_data:
        accept
                message         = Virus found: $malware_name
                malware         = *
                set acl_m0      = $malware_name

[...]

begin routers

virus_delivery:
        driver          = redirect
        data            = virus-quarantine@???
        condition       = ${if eq{$acl_m0}{} {no}{yes} }
        headers_remove  = Subject
        headers_add     = Subject: [Virus] $h_Subject: \nX-Virus-Status: Infected with $acl_m0
        domains         = *

Such construction works, but there is annoying issue:
headers Subject: and X-Virus-Status: is always been added twice.

Can anybody show me the way to solve this issue? I'm using SA-Exim 4.50.

Thanks in advance, 
    Alexander

-- 
Kind Regards,    Alexander Shikoff
minotaur@???
Mob.: +380 67 946 31 49