Schema does not understand quoted fieldnames in CHECK on PostgreSQL

I'm getting mismatch reports on timestamp fields (which module is insisting on unsigned timestamp fields, I'm not sure):

Mismatch (2)
Tables for which the schema and database are different.
node
*
node_counter
o column timestamp - difference on: unsigned
declared: array('description' => t('TODO: please describe this field!'), 'type' => 'int', 'unsigned' => TRUE, 'not null' => TRUE, 'default' => 0)
actual: array('description' => t('TODO: please describe this field!'), 'type' => 'int', 'not null' => TRUE, 'default' => 0)

system
*
files
o column timestamp - difference on: unsigned
declared: array('description' => t('TODO: please describe this field!'), 'type' => 'int', 'unsigned' => TRUE, 'not null' => TRUE, 'default' => 0)
actual: array('description' => t('TODO: please describe this field!'), 'type' => 'int', 'not null' => TRUE, 'default' => 0)

This is on a PostgreSQL database, where timestamp is a reserved word. PostgreSQL doesn't have a native unsigned integer, you just have to put a >= 0 check on it. The check for a timestamp field looks like

CHECK ("timestamp" >= 0);

other 'unsigned integer' fields produce a check like:

CHECK (fid >= 0);

The difference is the quoting of the fieldname. Evidently Schema isn't prepared to deal with the quoted fieldname, and so doesn't recognize that the constraint is actually in place.