[Exim] problem getting a condition right

I am momentarily blind, and need help ;-)
The following condition is getting me bald ...

condition         = "${if and { \
                      {!def:h_X-Spam-Flag:} \
                      {!def:h_X-DSPAM-Check:} \
                      {!eq {$received_protocol}{local}} \
                      {!eq {$sender_address_domain}{$domain}} \
                      ${lookup{$local_part@$domain}lsearch{/usr/local/etc/exim/mail_backup_users}}
                      }
                     {1}{0}

... my problem is on the 3rd last condition ....
on the lookup. I just can't figure it out though exim -be tells me....

        cheers
       - wash
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