diff --git a/CRM/Core/BAO/CustomGroup.php b/CRM/Core/BAO/CustomGroup.php
index 44c4e958c0f8..9f18bfde45b2 100644
--- a/CRM/Core/BAO/CustomGroup.php
+++ b/CRM/Core/BAO/CustomGroup.php
@@ -45,36 +45,13 @@ public static function create(&$params) {
       $group->title = $params['title'];
     }
 
-    $extends = CRM_Utils_Array::value('extends', $params, []);
-    $extendsEntity = $extends[0] ?? NULL;
-
-    $participantEntities = [
-      'ParticipantRole',
-      'ParticipantEventName',
-      'ParticipantEventType',
-    ];
-
-    if (in_array($extendsEntity, $participantEntities)) {
-      $group->extends = 'Participant';
-    }
-    else {
-      $group->extends = $extendsEntity;
-    }
-
-    $group->extends_entity_column_id = 'null';
-    if (in_array($extendsEntity, $participantEntities)
-    ) {
-      $group->extends_entity_column_id = CRM_Core_DAO::getFieldValue('CRM_Core_DAO_OptionValue', $extendsEntity, 'value', 'name');
-    }
-
-    // this is format when form get submit.
-    $extendsChildType = $extends[1] ?? NULL;
+    $extendsChildType = NULL;
     // lets allow user to pass direct child type value, CRM-6893
     if (!empty($params['extends_entity_column_value'])) {
       $extendsChildType = $params['extends_entity_column_value'];
     }
     if (!CRM_Utils_System::isNull($extendsChildType)) {
-      $registeredSubTypes = self::getSubTypes()[$extendsEntity];
+      $registeredSubTypes = self::getSubTypes()[$params['extends']];
       if (is_array($extendsChildType)) {
         foreach ($extendsChildType as $childType) {
           if (!array_key_exists($childType, $registeredSubTypes) && !in_array($childType, $registeredSubTypes, TRUE)) {
@@ -88,8 +65,8 @@ public static function create(&$params) {
         }
         $extendsChildType = [$extendsChildType];
       }
-      $extendsChildType = implode(CRM_Core_DAO::VALUE_SEPARATOR, (array) $extendsChildType);
-      if (CRM_Utils_Array::value(0, $extends) == 'Relationship') {
+      $extendsChildType = implode(CRM_Core_DAO::VALUE_SEPARATOR, $extendsChildType);
+      if ($params['extends'] == 'Relationship') {
         $extendsChildType = str_replace(['_a_b', '_b_a'], [
           '',
           '',
@@ -121,6 +98,8 @@ public static function create(&$params) {
       'is_active',
       'is_multiple',
       'icon',
+      'extends_entity_column_id',
+      'extends',
     ];
     $current_db_version = CRM_Core_BAO_Domain::version();
     $is_public_version = version_compare($current_db_version, '4.7.19', '>=');
@@ -214,7 +193,7 @@ public static function create(&$params) {
         $params['id'],
         'table_name'
       );
-      CRM_Core_BAO_SchemaHandler::changeFKConstraint($table, self::mapTableName($extendsEntity));
+      CRM_Core_BAO_SchemaHandler::changeFKConstraint($table, self::mapTableName($params['extends']));
     }
     $transaction->commit();
 
diff --git a/CRM/Custom/Form/Group.php b/CRM/Custom/Form/Group.php
index 2b1cf9158eeb..ddf49e1c3a80 100644
--- a/CRM/Custom/Form/Group.php
+++ b/CRM/Custom/Form/Group.php
@@ -413,7 +413,8 @@ public function postProcess() {
       $params['created_date'] = date('YmdHis');
     }
 
-    $group = CRM_Core_BAO_CustomGroup::create($params);
+    $result = civicrm_api3('CustomGroup', 'create', $params);
+    $group = $result['values'][$result['id']];
 
     // reset the cache
     Civi::cache('fields')->flush();
@@ -421,14 +422,14 @@ public function postProcess() {
     CRM_Core_BAO_Cache::resetCaches();
 
     if ($this->_action & CRM_Core_Action::UPDATE) {
-      CRM_Core_Session::setStatus(ts('Your custom field set \'%1 \' has been saved.', [1 => $group->title]), ts('Saved'), 'success');
+      CRM_Core_Session::setStatus(ts('Your custom field set \'%1 \' has been saved.', [1 => $group['title']]), ts('Saved'), 'success');
     }
     else {
       // Jump directly to adding a field if popups are disabled
       $action = CRM_Core_Resources::singleton()->ajaxPopupsEnabled ? '' : '/add';
-      $url = CRM_Utils_System::url("civicrm/admin/custom/group/field$action", 'reset=1&new=1&gid=' . $group->id . '&action=' . ($action ? 'add' : 'browse'));
+      $url = CRM_Utils_System::url("civicrm/admin/custom/group/field$action", 'reset=1&new=1&gid=' . $group['id'] . '&action=' . ($action ? 'add' : 'browse'));
       CRM_Core_Session::setStatus(ts("Your custom field set '%1' has been added. You can add custom fields now.",
-        [1 => $group->title]
+        [1 => $group['title']]
       ), ts('Saved'), 'success');
       $session = CRM_Core_Session::singleton();
       $session->replaceUserContext($url);
diff --git a/api/v3/CustomGroup.php b/api/v3/CustomGroup.php
index 3c5519fc706f..f45c9ca3028b 100644
--- a/api/v3/CustomGroup.php
+++ b/api/v3/CustomGroup.php
@@ -40,6 +40,29 @@ function civicrm_api3_custom_group_create($params) {
 
     return civicrm_api3_create_error("First item in params['extends'] must be a class name (e.g. 'Contact').");
   }
+  if (!isset($params['extends_entity_column_value']) && isset($params['extends'][1])) {
+    $extendsEntity = $params['extends'][0] ?? NULL;
+    $participantEntities = [
+      'ParticipantRole',
+      'ParticipantEventName',
+      'ParticipantEventType',
+    ];
+    $params['extends_entity_column_id'] = 'null';
+    if (in_array($extendsEntity, $participantEntities)
+    ) {
+      $params['extends_entity_column_id'] = CRM_Core_DAO::getFieldValue('CRM_Core_DAO_OptionValue', $extendsEntity, 'value', 'name');
+    }
+    $params['extends_entity_column_value'] = $params['extends'][1];
+    if (in_array($extendsEntity, $participantEntities)) {
+      $params['extends'] = 'Participant';
+    }
+    else {
+      $params['extends'] = $extendsEntity;
+    }
+  }
+  elseif (isset($params['extends']) && (!isset($params['extends'][1]) || empty($params['extends'][1]))) {
+    $params['extends'] = $params['extends'][0];
+  }
   if (isset($params['extends_entity_column_value']) && !is_array($params['extends_entity_column_value'])) {
     // BAO fails if this is a string, but API getFields says this must be a string, so we'll do a double backflip
     $params['extends_entity_column_value'] = CRM_Utils_Array::explodePadded($params['extends_entity_column_value']);