diff --git a/src/QUI/Memberships/Events.php b/src/QUI/Memberships/Events.php
index 28165c6d74055c9b73f2f39789c121c7580414b8..4d91eec1165dc5c91cb5714f6c098aa612c07039 100644
--- a/src/QUI/Memberships/Events.php
+++ b/src/QUI/Memberships/Events.php
@@ -186,6 +186,11 @@ protected static function createProductFields()
                 QUI\System\Log::addError(self::class . ' :: createProductFields');
                 QUI\System\Log::writeException($Exception);
             }
+        } elseif (!($MembershipField instanceof MembershipField)) {
+            QUI\System\Log::addError(
+                'quiqqer/memberships :: Cannot create memership field because product field with ID ' .
+                $MembershipField->getId() . ' is not a membership field.'
+            );
         }
 
         // Membership flag field (create new one is not configured)
diff --git a/src/QUI/Memberships/Handler.php b/src/QUI/Memberships/Handler.php
index aa68cf46a66db2a52330fc8ec25aa5873c1c9949..24fa83af8c37b9fbfbee1980c10c65375f620ac8 100644
--- a/src/QUI/Memberships/Handler.php
+++ b/src/QUI/Memberships/Handler.php
@@ -66,7 +66,7 @@ public function createChild($data = []): QUI\CRUD\Child
 
         foreach ($groupIds as $groupId) {
             // check if group exist by getting them
-            $Groups->get((int)$groupId);
+            $Groups->get($groupId);
         }
 
         $data['groupIds'] = ',' . implode(',', $groupIds) . ',';