Error when trying to change workflow states to a custom "published" workflow state

Drupal 8.4.0
Workbench Moderation (tried both 1.2 and 1.x-dev)

I created a custom workflow state called "Submitted" to replace "Published".

I set up a workflow transition called "Submit" to move between "draft" and "submitted".

If I create a node with the workflow applied, save the node as a draft, then attempt to re-edit and use the "submit" transition, the following error is logged.

Drupal\Core\Entity\EntityStorageException: Unable to apply data selector 'moderation_state.value' at 'moderation_state.value': Property value is unknown. in Drupal\Core\Entity\Sql\SqlContentEntityStorage->save() (line 805 of /var/www/html/core/lib/Drupal/Core/Entity/Sql/SqlContentEntityStorage.php).