TYPO3 Core

Given a TCA field of the type "select", with the renderMode set to "tree" and maxitems set to "1", the tree non-functional. No item at all can be selected. If maxitems is set to "2", two items can be selected, as would be expected.

Sample TCA:

        'tree_foo' => array(
            'exclude' => 0,
            'label' => 'LLL:EXT:foo_bar/Resources/Private/Language/locallang_db.xlf:tx_foobar_domain_model_qux.tree_foo',
            'config' => array(
                'type' => 'select',
                'foreign_table' => 'pages',
                'foreign_table_where' => 'ORDER BY pages.sorting ASC',
                'maxitems' => 1,
                'renderMode' => 'tree',
                'autoSizeMax' => 40,
                'treeConfig' => array(
                    'appearance' => array(
                        'expandAll' => 1,
                        'showHeader' => 1,
                        'maxLevels' => 20,
                        'width' => 600
                    ),
                    'parentField' => 'pid',
                ),
            ),
        ),

Tested on TYPO3 CMS 7.6-dev (git revision 2692580)