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### Expected Behavior:


### Actual Behavior:


### Steps to reproduce (I have confirmed I can reproduce this issue on the trunk branch):

1.
2.

### CMB2 Field Registration Code:

```php
add_action( 'cmb2_admin_init', 'yourprefix_register_demo_metabox' );
function yourprefix_register_demo_metabox() {

	$cmb = new_cmb2_box( array(
		// Box Config...
	) );

	$cmb->add_field( array(
		// Field Config...
	) );

	// Additional fields...
}
```