[Dovecot] dovecot-lda & sieve returns undefined symbol: deliver_mail

When I fire up dovecot, this is what I get with the following plugins enabled from dovecot.conf:

mail_plugins = cmusieve mail_plugin_dir = /dc/dovecot/lib/dovecot/lda

Here's the error:

Edlopen(/dc/dovecot/lib/dovecot/lda/lib90_cmusieve_plugin.so) failed: /dc/dovecot/lib/dovecot/lda/lib90_cmusieve_plugin.so: undefined symbol: deliver_mail Error: imap dump-capability process returned 89

Host is Ubuntu 6.06-1 AMD64, mailer is postfix.

Anybody have any ideas? Otherwise works fine if I comment out the plugins.

Thanks.