diff --git a/app/Invoice/Actions/MassStoreAction.php b/app/Invoice/Actions/MassStoreAction.php
index d11b8ea4..2ac28196 100644
--- a/app/Invoice/Actions/MassStoreAction.php
+++ b/app/Invoice/Actions/MassStoreAction.php
@@ -43,7 +43,7 @@ class MassStoreAction
 
             $invoice = Invoice::createFromFactory($factory);
             $invoice->save();
-            $invoice->positions()->createMany($invoice->positions->toArray());
+            $invoice->positions()->createMany($invoice->positions);
             $invoices->push($invoice->fresh('positions'));
         }
 
diff --git a/app/Invoice/Actions/MemberNewInvoiceAction.php b/app/Invoice/Actions/MemberNewInvoiceAction.php
index 5017a68e..4e5a375f 100644
--- a/app/Invoice/Actions/MemberNewInvoiceAction.php
+++ b/app/Invoice/Actions/MemberNewInvoiceAction.php
@@ -40,7 +40,7 @@ class MemberNewInvoiceAction
         return [
             ...$invoice->getAttributes(),
             'to' => $invoice->to,
-            'positions' => $invoice->getRelationValue('positions')->toArray(),
+            'positions' => $invoice->getRelationValue('positions'),
         ];
     }
 
diff --git a/app/Invoice/Data/PositionData.php b/app/Invoice/Data/PositionData.php
index 6a026601..c75a6779 100644
--- a/app/Invoice/Data/PositionData.php
+++ b/app/Invoice/Data/PositionData.php
@@ -2,6 +2,7 @@
 
 namespace App\Invoice\Data;
 
+use Spatie\LaravelData\Attributes\MapOutputName;
 use Spatie\LaravelData\Data;
 
 class PositionData extends Data
@@ -9,6 +10,7 @@ class PositionData extends Data
     public function __construct(
         public string $description,
         public string $price,
+        #[MapOutputName('member_id')]
         public int $memberId,
     ) {}
 }
diff --git a/app/Member/Factories/MemberInvoiceFactory.php b/app/Member/Factories/MemberInvoiceFactory.php
index 3f749f6e..5f899878 100644
--- a/app/Member/Factories/MemberInvoiceFactory.php
+++ b/app/Member/Factories/MemberInvoiceFactory.php
@@ -81,8 +81,7 @@ class MemberInvoiceFactory implements InvoiceCreator
                 $positions->push(PositionData::from([
                     'description' => str($child->name)->replace('{name}', $member->firstname . ' ' . $member->lastname)->replace('{year}', (string) $this->year),
                     'price' => $child->amount,
-                    /** @todo check if this is correct */
-                    'member_id' => $member->id,
+                    'memberId' => $member->id,
                     'id' => null,
                 ]));
             }