[exim] Tainted filename for search

Hi folks

I have an issue that only appears when using 4.94. I use this to lookup
dkim information for signing outgoing emails

  dkim_selector = ${lookup sqlite {/usr/exim/dkimcertificates select
selector from dkimcerts where domain='$sender_address_domain'}{$value}}
  dkim_private_key = ${lookup sqlite {/usr/exim/dkimcertificates select
cert from dkimcerts where domain='$sender_address_domain'}{$value}}


I get this message in my log

Tainted filename for search: '/usr/exim/dkimcertificates'

Does anybody have any idea how to fix this? Works in 4.93.

Rgds