drupal_write_record() handed third (undefined) parameter

I was getting a bunch of mysterious database errors -- telling me that the format column was a primary key (!)

Upon closer inspection I saw line 57 of excerpt.module:

drupal_write_record('excerpt', $excerpt, $primary_keys);

But $primary_keys is never defined anywhere. I believe that line should read:

drupal_write_record('excerpt', $excerpt, 'vid');