diff --git a/CRM/Core/BAO/CustomGroup.php b/CRM/Core/BAO/CustomGroup.php
index c00e866270ed..e5dbb35f718b 100644
--- a/CRM/Core/BAO/CustomGroup.php
+++ b/CRM/Core/BAO/CustomGroup.php
@@ -18,7 +18,15 @@
 /**
  * Business object for managing custom data groups.
  */
-class CRM_Core_BAO_CustomGroup extends CRM_Core_DAO_CustomGroup {
+class CRM_Core_BAO_CustomGroup extends CRM_Core_DAO_CustomGroup implements \Civi\Core\HookInterface {
+
+  /**
+   * @param \Civi\Core\Event\PostEvent $e
+   * @see CRM_Utils_Hook::post()
+   */
+  public static function self_hook_civicrm_post(\Civi\Core\Event\PostEvent $e): void {
+    Civi::cache('metadata')->flush();
+  }
 
   /**
    * Takes an associative array and creates a custom group object.
diff --git a/tests/phpunit/api/v4/Action/CustomValueTest.php b/tests/phpunit/api/v4/Action/CustomValueTest.php
index 337cc3c5903a..f774d3acce8e 100644
--- a/tests/phpunit/api/v4/Action/CustomValueTest.php
+++ b/tests/phpunit/api/v4/Action/CustomValueTest.php
@@ -263,4 +263,36 @@ public function testCRUD() {
     $this->assertEquals(0, count($result));
   }
 
+  /**
+   * Whenever a CustomGroup toggles the `is_multiple` flag, the entity-list should be updated.
+   *
+   * @throws \API_Exception
+   * @throws \Civi\API\Exception\UnauthorizedException
+   */
+  public function testEntityRefresh() {
+    $groupName = uniqid('groupc');
+
+    $this->assertNotContains("Custom_$groupName", Entity::get()->execute()->column('name'));
+
+    CustomGroup::create(FALSE)
+      ->addValue('title', $groupName)
+      ->addValue('extends', 'Contact')
+      ->addValue('is_multiple', FALSE)
+      ->execute();
+
+    $this->assertNotContains("Custom_$groupName", Entity::get()->execute()->column('name'));
+
+    CustomGroup::update(FALSE)
+      ->addWhere('name', '=', $groupName)
+      ->addValue('is_multiple', TRUE)
+      ->execute();
+    $this->assertContains("Custom_$groupName", Entity::get()->execute()->column('name'));
+
+    CustomGroup::update(FALSE)
+      ->addWhere('name', '=', $groupName)
+      ->addValue('is_multiple', FALSE)
+      ->execute();
+    $this->assertNotContains("Custom_$groupName", Entity::get()->execute()->column('name'));
+  }
+
 }