Deactivating a Select custom field and then reactiving doesn't let you re-use the existing select options

Create a custom field group.
Make a custom field of type alphanumeric select
Create a new set of options for the field
Save
Go back to the custom field and make it inactive (not the group, just the field)
Now try to reactivate the field. The previous set of options is no longer available. The database tables still contain all the appropriate entries, just this form is not displaying the option group.