diff --git a/app/code/Magento/Sales/Model/OrderRepository.php b/app/code/Magento/Sales/Model/OrderRepository.php
index ecd4e7babb1e3..a600d1489857c 100644
--- a/app/code/Magento/Sales/Model/OrderRepository.php
+++ b/app/code/Magento/Sales/Model/OrderRepository.php
@@ -157,6 +157,9 @@ public function get($id)
     private function setOrderTaxDetails(OrderInterface $order)
     {
         $extensionAttributes = $order->getExtensionAttributes();
+        if ($extensionAttributes === null) {
+            $extensionAttributes = $this->orderExtensionFactory->create();
+        }
         $orderTaxDetails = $this->orderTaxManagement->getOrderTaxDetails($order->getEntityId());
         $appliedTaxes = $orderTaxDetails->getAppliedTaxes();
 
@@ -180,6 +183,9 @@ private function setOrderTaxDetails(OrderInterface $order)
     private function setPaymentAdditionalInfo(OrderInterface $order): void
     {
         $extensionAttributes = $order->getExtensionAttributes();
+        if ($extensionAttributes === null) {
+            $extensionAttributes = $this->orderExtensionFactory->create();
+        }
         $paymentAdditionalInformation = $order->getPayment()->getAdditionalInformation();
 
         $objects = [];
diff --git a/app/code/Magento/Sales/Test/Unit/Model/OrderRepositoryTest.php b/app/code/Magento/Sales/Test/Unit/Model/OrderRepositoryTest.php
index 84c66d12c10d8..2e51bd8d75b89 100644
--- a/app/code/Magento/Sales/Test/Unit/Model/OrderRepositoryTest.php
+++ b/app/code/Magento/Sales/Test/Unit/Model/OrderRepositoryTest.php
@@ -18,12 +18,13 @@
 use Magento\Sales\Api\Data\OrderInterface;
 use Magento\Sales\Api\Data\OrderPaymentInterface;
 use Magento\Sales\Api\Data\OrderSearchResultInterfaceFactory as SearchResultFactory;
+use Magento\Sales\Model\Order;
 use Magento\Sales\Model\Order\Shipping;
 use Magento\Sales\Model\Order\ShippingAssignment;
 use Magento\Sales\Model\Order\ShippingAssignmentBuilder;
 use Magento\Sales\Model\OrderRepository;
 use Magento\Sales\Model\ResourceModel\Metadata;
-use Magento\Sales\Model\ResourceModel\Order;
+use Magento\Sales\Model\ResourceModel\Order as OrderResource;
 use Magento\Sales\Model\ResourceModel\Order\Collection;
 use Magento\Tax\Api\Data\OrderTaxDetailsInterface;
 use Magento\Tax\Api\OrderTaxManagementInterface;
@@ -70,6 +71,11 @@ class OrderRepositoryTest extends TestCase
      */
     private $paymentAdditionalInfoFactory;
 
+    /**
+     * @var OrderExtensionFactory|\MockObject
+     */
+    private $orderExtensionFactoryMock;
+
     /**
      * Setup the test
      *
@@ -88,7 +94,7 @@ protected function setUp(): void
         $this->collectionProcessor = $this->createMock(
             CollectionProcessorInterface::class
         );
-        $orderExtensionFactoryMock = $this->getMockBuilder(OrderExtensionFactory::class)
+        $this->orderExtensionFactoryMock = $this->getMockBuilder(OrderExtensionFactory::class)
             ->disableOriginalConstructor()
             ->getMock();
         $this->orderTaxManagementMock = $this->getMockBuilder(OrderTaxManagementInterface::class)
@@ -103,7 +109,7 @@ protected function setUp(): void
                 'metadata' => $this->metadata,
                 'searchResultFactory' => $this->searchResultFactory,
                 'collectionProcessor' => $this->collectionProcessor,
-                'orderExtensionFactory' => $orderExtensionFactoryMock,
+                'orderExtensionFactory' => $this->orderExtensionFactoryMock,
                 'orderTaxManagement' => $this->orderTaxManagementMock,
                 'paymentAdditionalInfoFactory' => $this->paymentAdditionalInfoFactory
             ]
@@ -178,10 +184,10 @@ public function testGetList()
      */
     public function testSave()
     {
-        $mapperMock = $this->getMockBuilder(Order::class)
+        $mapperMock = $this->getMockBuilder(OrderResource::class)
             ->disableOriginalConstructor()
             ->getMock();
-        $orderEntity = $this->createMock(\Magento\Sales\Model\Order::class);
+        $orderEntity = $this->createMock(Order::class);
         $extensionAttributes = $this->getMockBuilder(OrderExtension::class)
             ->addMethods(['getShippingAssignments'])
             ->getMock();
@@ -207,4 +213,57 @@ public function testSave()
         $orderEntity->expects($this->any())->method('getEntityId')->willReturn(1);
         $this->orderRepository->save($orderEntity);
     }
+
+    /**
+     * Test for method get.
+     *
+     * @return void
+     */
+    public function testGet()
+    {
+        $orderId = 1;
+        $appliedTaxes = 'applied_taxes';
+        $items = 'items';
+        $paymentInfo = [];
+
+        $orderEntity = $this->createMock(Order::class);
+        $paymentMock = $this->getMockBuilder(OrderPaymentInterface::class)
+            ->disableOriginalConstructor()->getMockForAbstractClass();
+        $paymentMock->expects($this->once())->method('getAdditionalInformation')->willReturn($paymentInfo);
+        $orderExtension = $this->getMockBuilder(OrderExtension::class)
+            ->setMethods(
+                [
+                    'getShippingAssignments',
+                    'setAppliedTaxes',
+                    'setConvertingFromQuote',
+                    'setItemAppliedTaxes',
+                    'setPaymentAdditionalInfo'
+                ]
+            )
+            ->disableOriginalConstructor()
+            ->getMockForAbstractClass();
+        $orderExtension->expects($this->once())->method('getShippingAssignments')->willReturn(true);
+        $orderExtension->expects($this->once())->method('setAppliedTaxes')->with($appliedTaxes);
+        $orderExtension->expects($this->once())->method('setConvertingFromQuote')->with(true);
+        $orderExtension->expects($this->once())->method('setItemAppliedTaxes')->with($items);
+        $orderExtension->expects($this->once())->method('setPaymentAdditionalInfo')->with($paymentInfo);
+        $this->orderExtensionFactoryMock->expects($this->once())->method('create')->willReturn($orderExtension);
+        $orderEntity->expects($this->once())->method('load')->with($orderId)->willReturn($orderEntity);
+        $orderEntity->expects($this->exactly(2))->method('getEntityId')->willReturn($orderId);
+        $orderEntity->expects($this->once())->method('getPayment')->willReturn($paymentMock);
+        $orderEntity->expects($this->exactly(2))->method('setExtensionAttributes')->with($orderExtension);
+        $orderEntity->expects($this->exactly(3))
+            ->method('getExtensionAttributes')
+            ->willReturnOnConsecutiveCalls(null, $orderExtension, $orderExtension);
+        $this->metadata->expects($this->once())->method('getNewInstance')->willReturn($orderEntity);
+        $orderTaxDetailsMock = $this->getMockBuilder(OrderTaxDetailsInterface::class)
+            ->disableOriginalConstructor()
+            ->setMethods(['setAppliedTaxes'])->getMockForAbstractClass();
+        $orderTaxDetailsMock->expects($this->once())->method('getAppliedTaxes')->willReturn($appliedTaxes);
+        $orderTaxDetailsMock->expects($this->once())->method('getItems')->willReturn($items);
+        $this->orderTaxManagementMock->expects($this->atLeastOnce())->method('getOrderTaxDetails')
+            ->willReturn($orderTaxDetailsMock);
+
+        $this->orderRepository->get($orderId);
+    }
 }