diff --git a/src/Relation/BelongsTo.php b/src/Relation/BelongsTo.php
index 0f3e07ad..5342c502 100644
--- a/src/Relation/BelongsTo.php
+++ b/src/Relation/BelongsTo.php
@@ -140,6 +140,10 @@ private function shouldPull(Tuple $tuple, Tuple $rTuple): bool
         $noChanges = true;
         $toReference = [];
         foreach ($this->outerKeys as $i => $outerKey) {
+            if (!\array_key_exists($outerKey, $newData)) {
+                continue;
+            }
+
             $innerKey = $this->innerKeys[$i];
             if (!\array_key_exists($innerKey, $oldData) || $oldData[$innerKey] !== $newData[$outerKey]) {
                 return true;
diff --git a/tests/ORM/Functional/Driver/Common/Integration/Case428/CaseTest.php b/tests/ORM/Functional/Driver/Common/Integration/Case428/CaseTest.php
new file mode 100644
index 00000000..f5688ef1
--- /dev/null
+++ b/tests/ORM/Functional/Driver/Common/Integration/Case428/CaseTest.php
@@ -0,0 +1,150 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428;
+
+use Cycle\ORM\Select;
+use Cycle\ORM\Tests\Functional\Driver\Common\BaseTest;
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity\Order;
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity\PurchaseOrder;
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity\PurchaseOrderItem;
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\IntegrationTestTrait;
+use Cycle\ORM\Tests\Traits\TableTrait;
+
+abstract class CaseTest extends BaseTest
+{
+    use IntegrationTestTrait;
+    use TableTrait;
+
+    public function testSelect(): void
+    {
+        // Order 1
+        $order = (new Select($this->orm, Entity\Order::class))
+            ->load('items')
+            ->wherePK(1)
+            ->fetchOne();
+
+        // Check result
+        $this->assertInstanceOf(Entity\Order::class, $order);
+        $this->assertCount(2, $order->items);
+
+        // Order 2
+        $order = (new Select($this->orm, Entity\Order::class))
+            ->load('items')
+            ->wherePK(2)
+            ->fetchOne();
+
+        // Check result
+        $this->assertInstanceOf(Entity\Order::class, $order);
+        $this->assertCount(1, $order->items);
+    }
+
+    public function testSave(): void
+    {
+        /** @var Order $order */
+        $order = (new Select($this->orm, Entity\Order::class))
+            ->wherePK(1)
+            ->load('items')
+            ->fetchOne();
+
+        $purchaseOrder = new PurchaseOrder('PO001');
+        $orderItems = [];
+        foreach ($order->items as $orderItem) {
+            $purchaseOrderItem = new PurchaseOrderItem($orderItem->quantity);
+            $purchaseOrderItem->orderItem = $orderItem;
+            $purchaseOrder->items[] = $purchaseOrderItem;
+            $orderItem->purchaseOrder = $purchaseOrder;
+            $orderItem->status = 1;
+            $orderItems[] = $orderItem;
+        }
+
+        $this->save($purchaseOrder, ...$orderItems);
+    }
+
+    public function testCreate(): void
+    {
+        $order = new Entity\Order('O0101');
+        $purchaseOrder = new PurchaseOrder('PO101');
+
+        $orderItems = [];
+        for ($i = 0; $i < 20; $i++) {
+            $orderItem = new Entity\OrderItem('A' . $i, 1);
+            $orderItem->order = $order;
+            // $order->items[] = $orderItem;
+            $orderItem->purchaseOrder = $purchaseOrder;
+            $orderItems[] = $orderItem;
+        }
+
+        $this->save($order, $purchaseOrder, ...$orderItems);
+    }
+
+    public function setUp(): void
+    {
+        // Init DB
+        parent::setUp();
+        $this->makeTables();
+        $this->fillData();
+
+        $this->loadSchema(__DIR__ . '/schema.php');
+    }
+
+    private function makeTables(): void
+    {
+        // Make tables
+        $this->makeTable('order', [
+            'id' => 'primary', // autoincrement
+            'number' => 'string',
+        ]);
+
+        $this->makeTable('order_item', [
+            'id' => 'primary',
+            'order_id' => 'int',
+            'sku' => 'string',
+            'quantity' => 'int',
+            'purchase_order_id' => 'int,nullable',
+            'status' => 'int',
+        ]);
+
+        $this->makeTable('purchase_order', [
+            'id' => 'primary',
+            'number' => 'string',
+        ]);
+
+        $this->makeTable('purchase_order_item', [
+            'id' => 'primary',
+            'purchase_order_id' => 'int',
+            'order_item_id' => 'int,nullable',
+            'quantity' => 'int',
+        ]);
+
+        $this->makeFK('order_item', 'order_id', 'order', 'id', 'NO ACTION', 'CASCADE');
+
+        $this->makeFK('order_item', 'purchase_order_id', 'purchase_order', 'id', 'NO ACTION', 'CASCADE');
+
+        $this->makeFK('purchase_order_item', 'purchase_order_id', 'purchase_order', 'id', 'NO ACTION', 'CASCADE');
+
+        $this->makeFK('purchase_order_item', 'order_item_id', 'order_item', 'id', 'NO ACTION', 'CASCADE');
+    }
+
+    private function fillData(): void
+    {
+        $this->getDatabase()->table('order')->insertMultiple(
+            ['number'],
+            [
+                ['O001'],
+                ['O002'],
+                ['O003'],
+            ],
+        );
+        $this->getDatabase()->table('order_item')->insertMultiple(
+            ['order_id', 'sku', 'quantity', 'purchase_order_id', 'status'],
+            [
+                [1, 'A', 1, null, 0],
+                [1, 'B', 1, null, 0],
+                [2, 'A', 2, null, 0],
+                [3, 'B', 2, null, 0],
+            ],
+        );
+    }
+}
diff --git a/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/Order.php b/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/Order.php
new file mode 100644
index 00000000..9e841899
--- /dev/null
+++ b/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/Order.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity;
+
+class Order
+{
+
+    public ?int $id = null;
+    public string $number;
+    /** @var iterable<OrderItem> */
+    public iterable $items = [];
+
+    public function __construct(string $number)
+    {
+        $this->number = $number;
+    }
+}
diff --git a/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/OrderItem.php b/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/OrderItem.php
new file mode 100644
index 00000000..47944014
--- /dev/null
+++ b/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/OrderItem.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity;
+
+class OrderItem
+{
+    public ?int $id = null;
+
+    public string $sku;
+    public int $quantity = 1;
+    public int $status = 0;
+
+    public ?int $purchase_order_id = null;
+    public ?PurchaseOrder $purchaseOrder = null;
+
+    public int $order_id;
+    public Order $order;
+
+    public function __construct(string $sku, int $quantity = 1)
+    {
+        $this->sku = $sku;
+        $this->quantity = $quantity;
+    }
+}
diff --git a/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/PurchaseOrder.php b/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/PurchaseOrder.php
new file mode 100644
index 00000000..05b9e672
--- /dev/null
+++ b/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/PurchaseOrder.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity;
+
+class PurchaseOrder
+{
+    public ?int $id = null;
+    public string $number;
+
+    /** @var iterable<PurchaseOrderItem> */
+    public iterable $items = [];
+
+    public function __construct(string $number)
+    {
+        $this->number = $number;
+    }
+}
diff --git a/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/PurchaseOrderItem.php b/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/PurchaseOrderItem.php
new file mode 100644
index 00000000..ad8c2fb0
--- /dev/null
+++ b/tests/ORM/Functional/Driver/Common/Integration/Case428/Entity/PurchaseOrderItem.php
@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity;
+
+class PurchaseOrderItem
+{
+    public ?int $id = null;
+    public int $quantity = 1;
+
+    public int $purchase_order_id;
+    public PurchaseOrder $purchaseOrder;
+
+    public ?int $order_item_id = null;
+    public ?OrderItem $orderItem = null;
+
+    public function __construct(int $quantity = 1)
+    {
+        $this->quantity = $quantity;
+    }
+}
diff --git a/tests/ORM/Functional/Driver/Common/Integration/Case428/schema.php b/tests/ORM/Functional/Driver/Common/Integration/Case428/schema.php
new file mode 100644
index 00000000..11cc618b
--- /dev/null
+++ b/tests/ORM/Functional/Driver/Common/Integration/Case428/schema.php
@@ -0,0 +1,186 @@
+<?php
+
+declare(strict_types=1);
+
+use Cycle\ORM\Mapper\Mapper;
+use Cycle\ORM\Relation;
+use Cycle\ORM\Schema\GeneratedField;
+use Cycle\ORM\SchemaInterface as Schema;
+use Cycle\ORM\Select\Repository;
+use Cycle\ORM\Select\Source;
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity\Order;
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity\OrderItem;
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity\PurchaseOrder;
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\Entity\PurchaseOrderItem;
+
+return [
+    'order' => [
+        Schema::ENTITY => Order::class,
+        Schema::MAPPER => Mapper::class,
+        Schema::SOURCE => Source::class,
+        Schema::DATABASE => 'default',
+        Schema::TABLE => 'order',
+        Schema::PRIMARY_KEY => ['id'],
+        Schema::FIND_BY_KEYS => ['id'],
+        Schema::COLUMNS => [
+            'id' => 'id',
+            'number' => 'number',
+        ],
+        Schema::RELATIONS => [
+            'items' => [
+                Relation::TYPE => Relation::HAS_MANY,
+                Relation::TARGET => 'order_item',
+                Relation::COLLECTION_TYPE => 'array',
+                Relation::LOAD => Relation::LOAD_PROMISE,
+                Relation::SCHEMA => [
+                    Relation::CASCADE => true,
+                    Relation::NULLABLE => false,
+                    Relation::WHERE => [],
+                    Relation::ORDER_BY => [],
+                    Relation::INNER_KEY => ['id'],
+                    Relation::OUTER_KEY => 'order_id',
+                ],
+            ],
+        ],
+        Schema::TYPECAST => [
+            'id' => 'int',
+            'number' => 'string',
+        ],
+        Schema::SCHEMA => [],
+        Schema::GENERATED_FIELDS => [
+            'id' => GeneratedField::ON_INSERT, // autoincrement
+        ],
+    ],
+    'order_item' => [
+        Schema::ENTITY => OrderItem::class,
+        Schema::SOURCE => Source::class,
+        Schema::DATABASE => 'default',
+        Schema::MAPPER => Mapper::class,
+        Schema::TABLE => 'order_item',
+        Schema::PRIMARY_KEY => ['id'],
+        Schema::FIND_BY_KEYS => ['id'],
+        Schema::COLUMNS => [
+            'id' => 'id',
+            'order_id' => 'order_id',
+            'sku' => 'sku',
+            'quantity' => 'quantity',
+            'purchase_order_id' => 'purchase_order_id',
+            'status' => 'status',
+        ],
+        Schema::RELATIONS => [
+            'order' => [
+                Relation::TYPE => Relation::BELONGS_TO,
+                Relation::TARGET => 'order',
+                Relation::LOAD => Relation::LOAD_PROMISE,
+                Relation::SCHEMA => [
+                    Relation::CASCADE => true,
+                    Relation::NULLABLE => false,
+                    Relation::INNER_KEY => 'order_id',
+                    Relation::OUTER_KEY => ['id'],
+                ],
+            ],
+            'purchaseOrder' => [
+                Relation::TYPE => Relation::BELONGS_TO,
+                Relation::TARGET => 'purchase_order',
+                Relation::LOAD => Relation::LOAD_PROMISE,
+                Relation::SCHEMA => [
+                    Relation::CASCADE => true,
+                    Relation::NULLABLE => true,
+                    Relation::INNER_KEY => 'purchase_order_id',
+                    Relation::OUTER_KEY => ['id'],
+                ],
+            ],
+        ],
+        Schema::TYPECAST => [
+            'id' => 'int',
+            'order_id' => 'int',
+            'sku' => 'string',
+            'quantity' => 'int',
+            'purchase_order_id' => 'int',
+            'status' => 'int',
+        ],
+        Schema::SCHEMA => [],
+        Schema::GENERATED_FIELDS => [
+            'id' => GeneratedField::ON_INSERT, // autoincrement
+        ],
+    ],
+    'purchase_order' => [
+        Schema::ENTITY => PurchaseOrder::class,
+        Schema::MAPPER => Mapper::class,
+        Schema::SOURCE => Source::class,
+        Schema::REPOSITORY => Repository::class,
+        Schema::DATABASE => 'default',
+        Schema::TABLE => 'purchase_order',
+        Schema::PRIMARY_KEY => ['id'],
+        Schema::FIND_BY_KEYS => ['id'],
+        Schema::COLUMNS => [
+            'id' => 'id',
+            'number' => 'number',
+        ],
+        Schema::RELATIONS => [
+            'items' => [
+                Relation::TYPE => Relation::HAS_MANY,
+                Relation::TARGET => 'purchase_order_item',
+                Relation::COLLECTION_TYPE => 'array',
+                Relation::LOAD => Relation::LOAD_PROMISE,
+                Relation::SCHEMA => [
+                    Relation::CASCADE => true,
+                    Relation::NULLABLE => false,
+                    Relation::WHERE => [],
+                    Relation::ORDER_BY => [],
+                    Relation::INNER_KEY => ['id'],
+                    Relation::OUTER_KEY => 'purchase_order_id',
+                ],
+            ],
+        ],
+        Schema::SCOPE => null,
+        Schema::TYPECAST => [
+            'id' => 'int',
+            'number' => 'string',
+        ],
+        Schema::SCHEMA => [],
+        Schema::GENERATED_FIELDS => [
+            'id' => GeneratedField::ON_INSERT, // autoincrement
+        ],
+    ],
+    'purchase_order_item' => [
+        Schema::ENTITY => PurchaseOrderItem::class,
+        Schema::MAPPER => Mapper::class,
+        Schema::SOURCE => Source::class,
+        Schema::REPOSITORY => Repository::class,
+        Schema::DATABASE => 'default',
+        Schema::TABLE => 'purchase_order_item',
+        Schema::PRIMARY_KEY => ['id'],
+        Schema::FIND_BY_KEYS => ['id'],
+        Schema::COLUMNS => [
+            'id' => 'id',
+            'purchase_order_id' => 'purchase_order_id',
+            'order_item_id' => 'order_item_id',
+            'quantity' => 'quantity',
+        ],
+        Schema::RELATIONS => [
+            'orderItem' => [
+                Relation::TYPE => Relation::BELONGS_TO,
+                Relation::TARGET => 'order_item',
+                Relation::LOAD => Relation::LOAD_PROMISE,
+                Relation::SCHEMA => [
+                    Relation::CASCADE => true,
+                    Relation::NULLABLE => true,
+                    Relation::INNER_KEY => 'order_item_id',
+                    Relation::OUTER_KEY => ['id'],
+                ],
+            ],
+        ],
+        Schema::SCOPE => null,
+        Schema::TYPECAST => [
+            'id' => 'primary',
+            'purchase_order_id' => 'int',
+            'order_item_id' => 'int',
+            'quantity' => 'int',
+        ],
+        Schema::SCHEMA => [],
+        Schema::GENERATED_FIELDS => [
+            'id' => GeneratedField::ON_INSERT, // autoincrement
+        ],
+    ],
+];
diff --git a/tests/ORM/Functional/Driver/MySQL/Integration/Case428/CaseTest.php b/tests/ORM/Functional/Driver/MySQL/Integration/Case428/CaseTest.php
new file mode 100644
index 00000000..854c70ec
--- /dev/null
+++ b/tests/ORM/Functional/Driver/MySQL/Integration/Case428/CaseTest.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cycle\ORM\Tests\Functional\Driver\MySQL\Integration\Case428;
+
+// phpcs:ignore
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\CaseTest as CommonClass;
+
+/**
+ * @group driver
+ * @group driver-mysql
+ */
+class CaseTest extends CommonClass
+{
+    public const DRIVER = 'mysql';
+}
diff --git a/tests/ORM/Functional/Driver/Postgres/Integration/Case428/CaseTest.php b/tests/ORM/Functional/Driver/Postgres/Integration/Case428/CaseTest.php
new file mode 100644
index 00000000..0c453529
--- /dev/null
+++ b/tests/ORM/Functional/Driver/Postgres/Integration/Case428/CaseTest.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cycle\ORM\Tests\Functional\Driver\Postgres\Integration\Case428;
+
+// phpcs:ignore
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\CaseTest as CommonClass;
+
+/**
+ * @group driver
+ * @group driver-postgres
+ */
+class CaseTest extends CommonClass
+{
+    public const DRIVER = 'postgres';
+}
diff --git a/tests/ORM/Functional/Driver/SQLServer/Integration/Case428/CaseTest.php b/tests/ORM/Functional/Driver/SQLServer/Integration/Case428/CaseTest.php
new file mode 100644
index 00000000..2423222b
--- /dev/null
+++ b/tests/ORM/Functional/Driver/SQLServer/Integration/Case428/CaseTest.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cycle\ORM\Tests\Functional\Driver\SQLServer\Integration\Case428;
+
+// phpcs:ignore
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\CaseTest as CommonClass;
+
+/**
+ * @group driver
+ * @group driver-sqlserver
+ */
+class CaseTest extends CommonClass
+{
+    public const DRIVER = 'sqlserver';
+}
diff --git a/tests/ORM/Functional/Driver/SQLite/Integration/Case428/CaseTest.php b/tests/ORM/Functional/Driver/SQLite/Integration/Case428/CaseTest.php
new file mode 100644
index 00000000..fcc451fb
--- /dev/null
+++ b/tests/ORM/Functional/Driver/SQLite/Integration/Case428/CaseTest.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Cycle\ORM\Tests\Functional\Driver\SQLite\Integration\Case428;
+
+// phpcs:ignore
+use Cycle\ORM\Tests\Functional\Driver\Common\Integration\Case428\CaseTest as CommonClass;
+
+/**
+ * @group driver
+ * @group driver-sqlite
+ */
+class CaseTest extends CommonClass
+{
+    public const DRIVER = 'sqlite';
+}