TYPO3 Core

Given I have the following TCA field configuration:

        'multiple' => [
            'label' => 'Multiple',
            'config' => [
                'type' => 'group',
                'internal_type' => 'db',
                'allowed' => 'pages',
                'multiple' => true,
                'size' => 10,
            ],
        ],

When I select the same page multiple times in this record

I expect to be able to save the record without error and see the selected page multiple times in the select box

Actual result:

Exception is thrown: