Integrity constraint violation when adding billing rate

Error message:
PDOException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '2-0' for key 'PRIMARY': INSERT INTO {support_rate_role} (subid, rid) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1); Array ( [:db_insert_placeholder_0] => 2 [:db_insert_placeholder_1] => 0 ) in support_rates_admin_form_submit() (line 533 of (path to Drupal site)/sites/default/modules/support_timer/support_rates/support_rates.module).

Received the above when adding in a billing rate for the first time.