Domain Mapping not set up, not in database?

Probably an obvious issue, but the instructions are SO short and contain NO mention of the database, I have to ask. Can't find the answer anywhere.

I've followed the instructions and installed Domain Mapping. It's appearing correctly, although I haven't actually used it yet.

But in the logs, I'm seeing this constant error from Apache:

... WordPress database error Table 'fluttershow.wp_domain_mapping' doesn't exist for query SELECT domain FROM wp_domain_mapping WHERE blog_id = '5' ....

What gives? Indeed, the wp_domain_mapping table is not in the database, but I've not seen any instructions on getting it in there, nor apparently did WPMU do it for me. Help!