How to set "Default Value" in a custom selection field with a Selection Field Choice Set

[nomad-cyanide]

I am trying to set a default value for a custom field.
The field i type Selection and I have a selection field choice set defined.

The selection choice set is defined like this:

choice1:Rented to tenant
choice2:Leased to tenant
choice3:Owned by tenant

The problem comes when I try to set a "Default Value" for the custom field. Either it says my entered JSON is either invalid or this message:

Invalid default value "{'choice3': 'Owned by tenant'}": Invalid choice ({'choice3': 'Owned by tenant'}) for choice set ownership_choices.

The above message comes when I enter this JSON:

{
"choice3": "Owned by tenant"
}

I might just be a JSON noob, but I really can't see a solution to this myself. :(