diff --git a/spec/Command/Customer/UpdateCustomerSpec.php b/spec/Command/Customer/UpdateCustomerSpec.php
index e22f6bc92..fa2be81f9 100644
--- a/spec/Command/Customer/UpdateCustomerSpec.php
+++ b/spec/Command/Customer/UpdateCustomerSpec.php
@@ -4,17 +4,18 @@
 
 namespace spec\Sylius\ShopApiPlugin\Command\Customer;
 
+use DateTimeImmutable;
 use PhpSpec\ObjectBehavior;
 
 final class UpdateCustomerSpec extends ObjectBehavior
 {
-    function let(): void
+    function let(DateTimeImmutable $birthday): void
     {
         $this->beConstructedWith(
                 'Sherlock',
                 'Holmes',
                 'sherlock@holmes.com',
-                '2017-11-01',
+                $birthday,
                 'm',
                 '091231512512',
                 true
@@ -41,9 +42,9 @@ function it_has_gender(): void
         $this->gender()->shouldReturn('m');
     }
 
-    function it_has_birthday(): void
+    function it_has_birthday(DateTimeImmutable $birthday): void
     {
-        $this->birthday()->shouldReturn('2017-11-01');
+        $this->birthday()->shouldReturn($birthday);
     }
 
     function it_has_phone_number(): void
diff --git a/spec/Handler/Customer/UpdateCustomerHandlerSpec.php b/spec/Handler/Customer/UpdateCustomerHandlerSpec.php
index 8ed6424ad..e8a55fdb6 100644
--- a/spec/Handler/Customer/UpdateCustomerHandlerSpec.php
+++ b/spec/Handler/Customer/UpdateCustomerHandlerSpec.php
@@ -4,6 +4,7 @@
 
 namespace spec\Sylius\ShopApiPlugin\Handler\Customer;
 
+use DateTimeImmutable;
 use PhpSpec\ObjectBehavior;
 use Sylius\Component\Core\Model\CustomerInterface;
 use Sylius\Component\Resource\Repository\RepositoryInterface;
@@ -23,6 +24,8 @@ function it_updates_customer(
         RepositoryInterface $customerRepository,
         CustomerInterface $customer
     ): void {
+        $birthday = new DateTimeImmutable('2019-02-10 10:22:00');
+
         $customerRepository->findOneBy(['email' => 'sherlock@holmes.com'])->willReturn($customer);
 
         $customer->getId()->willReturn('USER_ID');
@@ -30,7 +33,7 @@ function it_updates_customer(
         $customer->setFirstName('Sherlock')->shouldBeCalled();
         $customer->setLastName('Holmes')->shouldBeCalled();
         $customer->setEmail('sherlock@holmes.com')->shouldBeCalled();
-        $customer->setBirthday(new \DateTimeImmutable('2017-11-01'))->shouldBeCalled();
+        $customer->setBirthday($birthday)->shouldBeCalled();
         $customer->setGender('m')->shouldBeCalled();
         $customer->setPhoneNumber('091231512512')->shouldBeCalled();
         $customer->setSubscribedToNewsletter(true)->shouldBeCalled();
@@ -42,7 +45,7 @@ function it_updates_customer(
                 'Sherlock',
                 'Holmes',
                 'sherlock@holmes.com',
-                '2017-11-01',
+                $birthday,
                 'm',
                 '091231512512',
                 true
diff --git a/src/Command/Customer/UpdateCustomer.php b/src/Command/Customer/UpdateCustomer.php
index 752449564..6f1737ba5 100644
--- a/src/Command/Customer/UpdateCustomer.php
+++ b/src/Command/Customer/UpdateCustomer.php
@@ -4,6 +4,7 @@
 
 namespace Sylius\ShopApiPlugin\Command\Customer;
 
+use DateTimeImmutable;
 use Sylius\ShopApiPlugin\Command\CommandInterface;
 
 class UpdateCustomer implements CommandInterface
@@ -17,7 +18,7 @@ class UpdateCustomer implements CommandInterface
     /** @var string */
     protected $email;
 
-    /** @var string|null */
+    /** @var DateTimeImmutable|null */
     protected $birthday;
 
     /** @var string */
@@ -29,7 +30,7 @@ class UpdateCustomer implements CommandInterface
     /** @var bool */
     protected $subscribedToNewsletter;
 
-    public function __construct(string $firstName, string $lastName, string $email, ?string $birthday, string $gender, ?string $phoneNumber, ?bool $subscribedToNewsletter)
+    public function __construct(string $firstName, string $lastName, string $email, ?DateTimeImmutable $birthday, string $gender, ?string $phoneNumber, ?bool $subscribedToNewsletter)
     {
         $this->firstName = $firstName;
         $this->lastName = $lastName;
@@ -55,7 +56,7 @@ public function email(): string
         return $this->email;
     }
 
-    public function birthday(): ?string
+    public function birthday(): ?\DateTimeImmutable
     {
         return $this->birthday;
     }
diff --git a/src/Handler/Customer/UpdateCustomerHandler.php b/src/Handler/Customer/UpdateCustomerHandler.php
index 53b81fd8f..94c565b7e 100644
--- a/src/Handler/Customer/UpdateCustomerHandler.php
+++ b/src/Handler/Customer/UpdateCustomerHandler.php
@@ -28,7 +28,7 @@ public function __invoke(UpdateCustomer $command): void
         $customer->setLastName($command->lastName());
         $customer->setEmail($command->email());
         $customer->setGender($command->gender());
-        $customer->setBirthday(new \DateTimeImmutable($command->birthday()));
+        $customer->setBirthday($command->birthday());
         $customer->setPhoneNumber($command->phoneNumber());
         $customer->setSubscribedToNewsletter($command->subscribedToNewsletter());
 
diff --git a/src/Request/Customer/UpdateCustomerRequest.php b/src/Request/Customer/UpdateCustomerRequest.php
index 8f61d7937..9f20224f1 100644
--- a/src/Request/Customer/UpdateCustomerRequest.php
+++ b/src/Request/Customer/UpdateCustomerRequest.php
@@ -4,7 +4,7 @@
 
 namespace Sylius\ShopApiPlugin\Request\Customer;
 
-use DateTimeInterface;
+use DateTimeImmutable;
 use Sylius\ShopApiPlugin\Command\CommandInterface;
 use Sylius\ShopApiPlugin\Command\Customer\UpdateCustomer;
 use Sylius\ShopApiPlugin\Request\RequestInterface;
@@ -21,7 +21,7 @@ class UpdateCustomerRequest implements RequestInterface
     /** @var string|null */
     protected $email;
 
-    /** @var DateTimeInterface|null */
+    /** @var DateTimeImmutable|null */
     protected $birthday;
 
     /** @var string */
@@ -39,6 +39,9 @@ protected function __construct(Request $request)
         $this->lastName = $request->request->get('lastName');
         $this->email = $request->request->get('email');
         $this->birthday = $request->request->get('birthday');
+        if ($this->birthday !== null) {
+            $this->birthday = new DateTimeImmutable($this->birthday);
+        }
         $this->gender = $request->request->get('gender');
         $this->phoneNumber = $request->request->get('phoneNumber');
         $this->subscribedToNewsletter = $request->request->getBoolean('subscribedToNewsletter') ?? false;
diff --git a/tests/Request/UpdateCustomerRequestTest.php b/tests/Request/UpdateCustomerRequestTest.php
index 6b085a0d5..f72daf4ff 100644
--- a/tests/Request/UpdateCustomerRequestTest.php
+++ b/tests/Request/UpdateCustomerRequestTest.php
@@ -4,6 +4,7 @@
 
 namespace Tests\Sylius\ShopApiPlugin\Request;
 
+use DateTimeImmutable;
 use PHPUnit\Framework\TestCase;
 use Sylius\ShopApiPlugin\Command\Customer\UpdateCustomer;
 use Sylius\ShopApiPlugin\Request\Customer\UpdateCustomerRequest;
@@ -30,7 +31,7 @@ public function it_creates_update_customer_command()
             'ivan',
             'Mts',
             'ivan.matas@locastic.com',
-            '2017-11-01',
+            new DateTimeImmutable('2017-11-01'),
             'm',
             '125125112',
             true))