diff --git a/typo3/sysext/backend/Configuration/SiteConfiguration/site_language.php b/typo3/sysext/backend/Configuration/SiteConfiguration/site_language.php
index 6299cd2026585895c31566b2532fd0293e9fc8d1..4870e5f7010568dde456f73ea20d0ba66275a245 100644
--- a/typo3/sysext/backend/Configuration/SiteConfiguration/site_language.php
+++ b/typo3/sysext/backend/Configuration/SiteConfiguration/site_language.php
@@ -371,7 +371,6 @@ return [
                     ['label' => 'cyan', 'value' => 'cyan', 'icon' => 'flags-cyan'],
                     ['label' => 'rainbow', 'value' => 'rainbow', 'icon' => 'flags-rainbow'],
                 ],
-                'maxitems' => 1,
                 'fieldWizard' => [
                     'selectIcons' => [
                         'disabled' => false,
diff --git a/typo3/sysext/core/Classes/Configuration/Tca/TcaPreparation.php b/typo3/sysext/core/Classes/Configuration/Tca/TcaPreparation.php
index 6f381b79c5e4df56e717953699b836d2f278beba..13ea356e7a0e1743efb72ac432174e05ffbbf49e 100644
--- a/typo3/sysext/core/Classes/Configuration/Tca/TcaPreparation.php
+++ b/typo3/sysext/core/Classes/Configuration/Tca/TcaPreparation.php
@@ -45,7 +45,9 @@ readonly class TcaPreparation
         $tca = $this->configureCategoryRelations($tca, $isFlexForm);
         $tca = $this->configureFileReferences($tca, $isFlexForm);
         $tca = $this->configureEmailSoftReferences($tca);
-        return $this->configureLinkSoftReferences($tca);
+        $tca = $this->configureLinkSoftReferences($tca);
+        $tca = $this->configureSelectSingle($tca);
+        return $tca;
     }
 
     /**
@@ -326,4 +328,26 @@ readonly class TcaPreparation
         }
         return $tca;
     }
+
+    /**
+     * Add "'maxitems' => 1" to all "'type' => 'select'" column fields with "'renderType' => 'selectSingle'".
+     */
+    protected function configureSelectSingle(array $tca): array
+    {
+        foreach ($tca as &$tableDefinition) {
+            if (!is_array($tableDefinition['columns'] ?? null)) {
+                continue;
+            }
+            foreach ($tableDefinition['columns'] as &$fieldConfig) {
+                if (($fieldConfig['config']['type'] ?? null) === 'select' && ($fieldConfig['config']['renderType'] ?? null) === 'selectSingle') {
+                    // Hard set/override: 'maxitems' to 1, since selectSingle - as the name suggests - only
+                    // allows a single item to be selected. Setting this config option allows to prevent
+                    // further checks for the renderType, which should be avoided.
+                    // @todo This should be solved by using a dedicated TCA type for selectSingle instead.
+                    $fieldConfig['config']['maxitems'] = 1;
+                }
+            }
+        }
+        return $tca;
+    }
 }
diff --git a/typo3/sysext/core/Configuration/TCA/pages.php b/typo3/sysext/core/Configuration/TCA/pages.php
index cb320bbe0cd4e65219a77a5a21a82356a95d237f..dc1214977b3fece5be9a3021917c79805f519177 100644
--- a/typo3/sysext/core/Configuration/TCA/pages.php
+++ b/typo3/sysext/core/Configuration/TCA/pages.php
@@ -647,7 +647,6 @@ return [
                         'renderType' => 'backendLayoutFromParentPage',
                     ],
                 ],
-                'maxitems' => 1,
                 'dbFieldLength' => 64,
             ],
         ],
@@ -668,7 +667,6 @@ return [
                         'disabled' => false,
                     ],
                 ],
-                'maxitems' => 1,
                 'dbFieldLength' => 64,
             ],
         ],
diff --git a/typo3/sysext/core/Configuration/TCA/sys_file.php b/typo3/sysext/core/Configuration/TCA/sys_file.php
index 40a090253dd6c5ad08543c3a02339bb61bd796e1..4389aa75cf2f3b1ea3b9397cfa00c37ba8ca697c 100644
--- a/typo3/sysext/core/Configuration/TCA/sys_file.php
+++ b/typo3/sysext/core/Configuration/TCA/sys_file.php
@@ -41,7 +41,6 @@ return [
                     ['label' => '', 'value' => 0],
                 ],
                 'foreign_table' => 'sys_file_storage',
-                'maxitems' => 1,
             ],
         ],
         'identifier' => [
diff --git a/typo3/sysext/core/Configuration/TCA/sys_file_metadata.php b/typo3/sysext/core/Configuration/TCA/sys_file_metadata.php
index 4f9c63f9569a60d6923677f89772cd153a3c7f29..4ed3f04e719b24bb6d090373a5b163f998c56d2a 100644
--- a/typo3/sysext/core/Configuration/TCA/sys_file_metadata.php
+++ b/typo3/sysext/core/Configuration/TCA/sys_file_metadata.php
@@ -50,7 +50,6 @@ return [
                 'foreign_table' => 'sys_file',
                 'foreign_table_where' => 'AND {#sys_file}.{#uid} = ###REC_FIELD_file###',
                 'minitems' => 1,
-                'maxitems' => 1,
                 'default' => 0,
             ],
         ],
diff --git a/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnattributeinline/Configuration/TCA/tx_testirremnattributeinline_hotel_offer_rel.php b/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnattributeinline/Configuration/TCA/tx_testirremnattributeinline_hotel_offer_rel.php
index 600968a215d7a6fbd7ef5e8c77d3eb73e771c3df..d0f4e1827afeae896c0f20343ed198eb84ec8bac 100644
--- a/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnattributeinline/Configuration/TCA/tx_testirremnattributeinline_hotel_offer_rel.php
+++ b/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnattributeinline/Configuration/TCA/tx_testirremnattributeinline_hotel_offer_rel.php
@@ -30,7 +30,6 @@ return [
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_testirremnattributeinline_hotel',
                 'foreign_table_where' => 'AND {#tx_testirremnattributeinline_hotel}.{#pid}=###CURRENT_PID### AND {#tx_testirremnattributeinline_hotel}.{#sys_language_uid}="###REC_FIELD_sys_language_uid###"',
-                'maxitems' => 1,
                 'default' => 0,
             ],
         ],
@@ -41,7 +40,6 @@ return [
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_testirremnattributeinline_offer',
                 'foreign_table_where' => 'AND {#tx_testirremnattributeinline_offer}.{#pid}=###CURRENT_PID### AND {#tx_testirremnattributeinline_offer}.{#sys_language_uid}="###REC_FIELD_sys_language_uid###"',
-                'maxitems' => 1,
                 'default' => 0,
             ],
         ],
diff --git a/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnattributesimple/Configuration/TCA/tx_testirremnattributesimple_hotel_offer_rel.php b/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnattributesimple/Configuration/TCA/tx_testirremnattributesimple_hotel_offer_rel.php
index 38ac4cd64405a718983ca98198c54fa9153f87e4..03a23571b3294520e52ed854dfc655feebb5e439 100644
--- a/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnattributesimple/Configuration/TCA/tx_testirremnattributesimple_hotel_offer_rel.php
+++ b/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnattributesimple/Configuration/TCA/tx_testirremnattributesimple_hotel_offer_rel.php
@@ -29,7 +29,6 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_testirremnattributesimple_hotel',
-                'maxitems' => 1,
                 'default' => 0,
             ],
         ],
@@ -39,7 +38,6 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_testirremnattributesimple_offer',
-                'maxitems' => 1,
                 'default' => 0,
             ],
         ],
diff --git a/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnsymmetric/Configuration/TCA/tx_testirremnsymmetric_hotel_rel.php b/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnsymmetric/Configuration/TCA/tx_testirremnsymmetric_hotel_rel.php
index 5db2f5b5c36f4739bbf911c4c36bdfc8327762c0..9d10e80d9c89bb5b42d12cc592284d8cc10b6315 100644
--- a/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnsymmetric/Configuration/TCA/tx_testirremnsymmetric_hotel_rel.php
+++ b/typo3/sysext/core/Tests/Functional/Fixtures/Extensions/test_irre_mnsymmetric/Configuration/TCA/tx_testirremnsymmetric_hotel_rel.php
@@ -29,7 +29,6 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_testirremnsymmetric_hotel',
-                'maxitems' => 1,
                 'default' => 0,
             ],
         ],
@@ -39,7 +38,6 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_testirremnsymmetric_hotel',
-                'maxitems' => 1,
                 'default' => 0,
             ],
         ],
diff --git a/typo3/sysext/core/Tests/Unit/Configuration/Tca/TcaPreparationTest.php b/typo3/sysext/core/Tests/Unit/Configuration/Tca/TcaPreparationTest.php
index 5860192372fda2d0fb9aa3f0eaa7e81fdb37a6a9..2e5383733995be82a22710d93f0683806f47c348 100644
--- a/typo3/sysext/core/Tests/Unit/Configuration/Tca/TcaPreparationTest.php
+++ b/typo3/sysext/core/Tests/Unit/Configuration/Tca/TcaPreparationTest.php
@@ -756,4 +756,11 @@ final class TcaPreparationTest extends UnitTestCase
         $subjectMethodReflection = new \ReflectionMethod($subject, 'prepareFileExtensions');
         self::assertEquals('jpg,png,gif', $subjectMethodReflection->invoke($subject, ['common-image-types,jpg,gif']));
     }
+
+    #[Test]
+    public function prepareSelectSingleAddsMaxItems(): void
+    {
+        $subject = (new TcaPreparation())->prepare(['foo' => ['columns' => ['select' => ['config' => ['type' => 'select', 'renderType' => 'selectSingle']]]]]);
+        self::assertEquals(1, $subject['foo']['columns']['select']['config']['maxitems']);
+    }
 }
diff --git a/typo3/sysext/extbase/Configuration/TCA/Overrides/fe_users.php b/typo3/sysext/extbase/Configuration/TCA/Overrides/fe_users.php
index 73223f02882d4b69deaac24349e868772f248c7b..91dd555e68be1f076edfe531e1a721721f894acc 100644
--- a/typo3/sysext/extbase/Configuration/TCA/Overrides/fe_users.php
+++ b/typo3/sysext/extbase/Configuration/TCA/Overrides/fe_users.php
@@ -18,7 +18,6 @@ if (!isset($GLOBALS['TCA']['fe_users']['ctrl']['type'])) {
                         ['label' => 'LLL:EXT:extbase/Resources/Private/Language/locallang_db.xlf:fe_users.tx_extbase_type.0', 'value' => '0'],
                         ['label' => 'LLL:EXT:extbase/Resources/Private/Language/locallang_db.xlf:fe_users.tx_extbase_type.Tx_Extbase_Domain_Model_FrontendUser', 'value' => 'Tx_Extbase_Domain_Model_FrontendUser'],
                     ],
-                    'maxitems' => 1,
                     'default' => 0,
                 ],
             ],
diff --git a/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/blog_example/Configuration/TCA/tx_blogexample_domain_model_post.php b/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/blog_example/Configuration/TCA/tx_blogexample_domain_model_post.php
index 511e0f83ec82259f808cc54079c0419597475a7d..364ef14b8f351bd3c5e8c8855e5f515984542831 100644
--- a/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/blog_example/Configuration/TCA/tx_blogexample_domain_model_post.php
+++ b/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/blog_example/Configuration/TCA/tx_blogexample_domain_model_post.php
@@ -41,7 +41,6 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_blogexample_domain_model_blog',
-                'maxitems' => 1,
             ],
         ],
         'title' => [
diff --git a/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/parent_child_translation/Configuration/TCA/tx_parentchildtranslation_domain_model_main.php b/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/parent_child_translation/Configuration/TCA/tx_parentchildtranslation_domain_model_main.php
index e136c631d2587899eb000dde4075f96b556a97ab..356ba159a1ef039cc9957cc387d3c2b7d8703b6e 100644
--- a/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/parent_child_translation/Configuration/TCA/tx_parentchildtranslation_domain_model_main.php
+++ b/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/parent_child_translation/Configuration/TCA/tx_parentchildtranslation_domain_model_main.php
@@ -44,8 +44,6 @@ return [
                 'foreign_table' => 'tx_parentchildtranslation_domain_model_child',
                 'foreign_table_where' => 'AND {#tx_parentchildtranslation_domain_model_child}.{#sys_language_uid} IN (0,-1)',
                 'default' => 0,
-                'minitems' => 0,
-                'maxitems' => 1,
             ],
         ],
         'squeeze' => [
diff --git a/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/parent_child_translation/Configuration/TCA/tx_parentchildtranslation_domain_model_squeeze.php b/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/parent_child_translation/Configuration/TCA/tx_parentchildtranslation_domain_model_squeeze.php
index bc6fac5930c86c6b88f6c817e49846d329d1c2af..2532cf2dafa7e5ee919ae465187dab544a26d777 100644
--- a/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/parent_child_translation/Configuration/TCA/tx_parentchildtranslation_domain_model_squeeze.php
+++ b/typo3/sysext/extbase/Tests/Functional/Fixtures/Extensions/parent_child_translation/Configuration/TCA/tx_parentchildtranslation_domain_model_squeeze.php
@@ -44,8 +44,6 @@ return [
                 'foreign_table' => 'tx_parentchildtranslation_domain_model_child',
                 'foreign_table_where' => 'AND {#tx_parentchildtranslation_domain_model_child}.{#sys_language_uid} IN (0,-1)',
                 'default' => 0,
-                'minitems' => 0,
-                'maxitems' => 1,
             ],
         ],
         'parent' => [
diff --git a/typo3/sysext/filemetadata/Configuration/TCA/Overrides/sys_file_metadata.php b/typo3/sysext/filemetadata/Configuration/TCA/Overrides/sys_file_metadata.php
index 94e04f2a9a09ed036e472faddf7ae2e268d88804..d24467d474fef83ff6bb70ca1da230da5950face 100644
--- a/typo3/sysext/filemetadata/Configuration/TCA/Overrides/sys_file_metadata.php
+++ b/typo3/sysext/filemetadata/Configuration/TCA/Overrides/sys_file_metadata.php
@@ -345,7 +345,6 @@ $tca = [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'minitems' => 1,
-                'maxitems' => 1,
                 'items' => [
                     ['label' => 0, 'value' => 0],
                     ['label' => 1, 'value' => 1],
diff --git a/typo3/sysext/frontend/Configuration/TCA/tt_content.php b/typo3/sysext/frontend/Configuration/TCA/tt_content.php
index cc32944ae8711183896f668def725e3e2ffbe996..765c3ea2925ee083ba889e83793249f234aa62a9 100644
--- a/typo3/sysext/frontend/Configuration/TCA/tt_content.php
+++ b/typo3/sysext/frontend/Configuration/TCA/tt_content.php
@@ -972,7 +972,6 @@ return [
             'config' => [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
-                'maxitems' => 1,
                 'itemsProcFunc' => \TYPO3\CMS\Core\Hooks\TcaItemsProcessorFunctions::class . '->populateAvailableCategoryFields',
                 'itemsProcConfig' => [
                     'table' => 'tt_content',
diff --git a/typo3/sysext/indexed_search/Configuration/TCA/index_config.php b/typo3/sysext/indexed_search/Configuration/TCA/index_config.php
index e229c4be869f49342c2ea631d05fd500643a5535..8f5254742ec3c869a9f3f2a409c7af79822a7093 100644
--- a/typo3/sysext/indexed_search/Configuration/TCA/index_config.php
+++ b/typo3/sysext/indexed_search/Configuration/TCA/index_config.php
@@ -43,7 +43,6 @@ return [
                     ['label' => 'LLL:EXT:indexed_search/Resources/Private/Language/locallang_db.xlf:index_config.type.I.4', 'value' => '4'],
                     ['label' => 'LLL:EXT:indexed_search/Resources/Private/Language/locallang_db.xlf:index_config.type.I.5', 'value' => '5'],
                 ],
-                'maxitems' => 1,
             ],
         ],
         'depth' => [
@@ -58,7 +57,6 @@ return [
                     ['label' => 'LLL:EXT:core/Resources/Private/Language/locallang_core.xlf:labels.depth_3', 'value' => '3'],
                     ['label' => 'LLL:EXT:core/Resources/Private/Language/locallang_core.xlf:labels.depth_4', 'value' => '4'],
                 ],
-                'maxitems' => 1,
             ],
         ],
         'table2index' => [
@@ -70,7 +68,6 @@ return [
                     ['label' => 'LLL:EXT:indexed_search/Resources/Private/Language/locallang_db.xlf:index_config.table2index.I.0', 'value' => '0'],
                 ],
                 'itemsProcFunc' => \TYPO3\CMS\IndexedSearch\Hook\AvailableTcaTables::class . '->populateTables',
-                'maxitems' => 1,
                 'dbFieldLength' => 255,
             ],
         ],
@@ -168,7 +165,6 @@ return [
                     ['label' => 'LLL:EXT:indexed_search/Resources/Private/Language/locallang_db.xlf:index_config.timer_frequency.I.1', 'value' => '86400'],
                     ['label' => 'LLL:EXT:indexed_search/Resources/Private/Language/locallang_db.xlf:index_config.timer_frequency.I.2', 'value' => '604800'],
                 ],
-                'maxitems' => 1,
                 'default' => 86400,
             ],
         ],
diff --git a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_displaycond.php b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_displaycond.php
index 74a1ff59ff49b348e1af07e6f63607b6a3b350e2..e42fbc7d34edd72335eeb233e8be6b6a5748fd62 100644
--- a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_displaycond.php
+++ b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_displaycond.php
@@ -31,8 +31,6 @@ return [
             'config' => [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
-                'size' => 1,
-                'maxitems' => 1,
                 'items' => [
                     ['label' => 'false values', 'value' => '--div--'],
                     ['label' => 'integer 0', 'value' => 0],
@@ -136,9 +134,6 @@ return [
                     ['label' => 'foo2', 'value' => 2],
                     ['label' => 'foo42', 'value' => 42],
                 ],
-                'size' => 1,
-                'minitems' => 0,
-                'maxitems' => 1,
             ],
         ],
         'checkbox_1' => [
@@ -270,9 +265,6 @@ return [
                     ['label' => 'Hide input_2 on flex_1', 'value' => 0],
                     ['label' => 'Show input_2 on flex_1', 'value' => 1],
                 ],
-                'size' => 1,
-                'minitems' => 0,
-                'maxitems' => 1,
             ],
         ],
         'flex_1' => [
diff --git a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_mn_mm.php b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_mn_mm.php
index 809a4a7d33ba36332eb436fb1e2e2c401896a54d..8358ac29d3232baa2359217d1621da3e9daa3530 100644
--- a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_mn_mm.php
+++ b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_mn_mm.php
@@ -29,7 +29,6 @@ return [
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_styleguide_inline_mn',
                 'foreign_table_where' => "AND {#tx_styleguide_inline_mn}.{#pid}=###CURRENT_PID### AND {#tx_styleguide_inline_mn}.{#sys_language_uid}='###REC_FIELD_sys_language_uid###'",
-                'maxitems' => 1,
                 'localizeReferences' => 1,
             ],
         ],
@@ -40,7 +39,6 @@ return [
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_styleguide_inline_mn_child',
                 'foreign_table_where' => "AND {#tx_styleguide_inline_mn_child}.{#pid}=###CURRENT_PID### AND {#tx_styleguide_inline_mn_child}.{#sys_language_uid}='###REC_FIELD_sys_language_uid###'",
-                'maxitems' => 1,
                 'localizeReferences' => 1,
             ],
         ],
diff --git a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_mnsymmetric_mm.php b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_mnsymmetric_mm.php
index 52c133f473f0023fcdffae516d562cb325d70850..bd6044c15f40f70950633245c9902187fcbd3b1b 100644
--- a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_mnsymmetric_mm.php
+++ b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_mnsymmetric_mm.php
@@ -28,7 +28,6 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_styleguide_inline_mnsymmetric',
-                'maxitems' => 1,
                 'localizeReferences' => 1,
             ],
         ],
@@ -38,7 +37,6 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_styleguide_inline_mnsymmetric',
-                'maxitems' => 1,
                 'localizeReferences' => 1,
             ],
         ],
diff --git a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombination_mm.php b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombination_mm.php
index 09dce5f9f6bf7e3cc172639704069e8ce413f7e7..0393919c873a6c911825811108c39c4236ff88fc 100644
--- a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombination_mm.php
+++ b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombination_mm.php
@@ -26,9 +26,7 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_styleguide_inline_usecombination',
-                'size' => 1,
                 'minitems' => 1,
-                'maxitems' => 1,
             ],
         ],
         'select_child' => [
@@ -37,9 +35,7 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_styleguide_inline_usecombination_child',
-                'size' => 1,
                 'minitems' => 1,
-                'maxitems' => 1,
             ],
         ],
     ],
diff --git a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombinationbox_mm.php b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombinationbox_mm.php
index aa7c65c8e2fc32e997a0cbf4be34a4793a8b1ab2..1398357d64e03307aa323760bc83107eb0ceffb5 100644
--- a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombinationbox_mm.php
+++ b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombinationbox_mm.php
@@ -27,9 +27,7 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_styleguide_inline_usecombinationbox',
-                'size' => 1,
                 'minitems' => 1,
-                'maxitems' => 1,
             ],
         ],
         'select_child' => [
@@ -38,9 +36,7 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_styleguide_inline_usecombinationbox_child',
-                'size' => 1,
                 'minitems' => 1,
-                'maxitems' => 1,
             ],
         ],
     ],
diff --git a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombinationgroup_mm.php b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombinationgroup_mm.php
index 6cd1e26268a76b8d585e7eb61259a829d19cf3db..e1e52e5d663120aabbe2e77587431d40951fce92 100644
--- a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombinationgroup_mm.php
+++ b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_inline_usecombinationgroup_mm.php
@@ -27,9 +27,7 @@ return [
                 'type' => 'select',
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_styleguide_inline_usecombinationgroup',
-                'size' => 1,
                 'minitems' => 1,
-                'maxitems' => 1,
             ],
         ],
         'group_child' => [
diff --git a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_required.php b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_required.php
index 793cfb2fb18b9f8a1dd8ac1ec36fc8ce893991b6..b1b747d4ffce3c82bb9670f8edfc49ac3a694f1b 100644
--- a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_required.php
+++ b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_required.php
@@ -91,10 +91,9 @@ return [
                     ['label' => 'foo2', 'value' => 2],
                     ['label' => 'foo3', 'value' => 3],
                 ],
-                // combination size > 1 & maxitems 1 triggers "singlebox" mode
+                // size > 1 triggers "singlebox" mode
                 'size' => 2,
                 'minitems' => 1,
-                'maxitems' => 1,
             ],
         ],
         'select_3' => [
diff --git a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_typeforeign.php b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_typeforeign.php
index 92b7fea72f3d54e2dde874ee01cf4c1b93ba97b3..a6b94b680780f310cf579e9113384e9f1448050e 100644
--- a/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_typeforeign.php
+++ b/typo3/sysext/styleguide/Configuration/TCA/tx_styleguide_typeforeign.php
@@ -31,8 +31,6 @@ return [
                 'renderType' => 'selectSingle',
                 'foreign_table' => 'tx_styleguide_type',
                 'minitems' => 1,
-                'maxitems' => 1,
-                'size' => 1,
             ],
         ],