[exim] ACL problem

Hi all,

I'm trying to add an ACL that accepts mail from certain networks
(listed in exim-priviledged). However upon starting Exim, I see the
following:

2005-04-25 14:19:48 failed to expand ""${if
${lookup{$sender_host_address}lsearch{/local/exim/etc/exim-priviledged}{yes}{no}}}""
while checking a list: condition name expected, but found
"${lookup{$sender"

The ACL contains the following line. I first thought that the "'s must
be required but still no joy. Am I missing something glaringly
obvious?

accept senders = "${if
${lookup{$sender_host_address}lsearch{/local/exim/etc/exim-priviledged}{yes}{no}}}"

Many thanks,

Doug