local_scan_path option error

I've previously used sa-exim statically built into exim on a Solaris 
machine.  Just undertook to do a Linux install with exim 4.30, and 
sa-exim 3.1, patching the exim source to dynamically load a .so file.  I 
added a local_scan_path option (at present, pointing to the accept.so 
module) to the main section of the config file, but testing the config 
file with exim -bV yields the following error:

2004-01-22 16:26:01 Exim configuration error in line 8 of 
/etc/mail/exim/exim.conf:
  main option "local_scan_path" unknown
2004-01-22 16:26:01 Exim configuration error in line 8 of 
/etc/mail/exim/exim.conf:
  main option "local_scan_path" unknown
2004-01-22 16:26:01 Exim configuration error in line 8 of 
/etc/mail/exim/exim.conf:
  main option "local_scan_path" unknown

Anybody know what I'm doing wrong?