diff --git a/src/Symfony/Bridge/Doctrine/Tests/Fixtures/AssociatedEntityDto.php b/src/Symfony/Bridge/Doctrine/Tests/Fixtures/AssociatedEntityDto.php
new file mode 100644
index 0000000000000..d6f82f8214846
--- /dev/null
+++ b/src/Symfony/Bridge/Doctrine/Tests/Fixtures/AssociatedEntityDto.php
@@ -0,0 +1,17 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Bridge\Doctrine\Tests\Fixtures;
+
+class AssociatedEntityDto
+{
+    public $singleId;
+}
diff --git a/src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueEntityValidatorTest.php b/src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueEntityValidatorTest.php
index f554acb70d0fb..9f0341bdc7794 100644
--- a/src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueEntityValidatorTest.php
+++ b/src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueEntityValidatorTest.php
@@ -21,6 +21,7 @@
 use Doctrine\Persistence\ObjectManager;
 use PHPUnit\Framework\MockObject\MockObject;
 use Symfony\Bridge\Doctrine\Tests\DoctrineTestHelper;
+use Symfony\Bridge\Doctrine\Tests\Fixtures\AssociatedEntityDto;
 use Symfony\Bridge\Doctrine\Tests\Fixtures\AssociationEntity;
 use Symfony\Bridge\Doctrine\Tests\Fixtures\AssociationEntity2;
 use Symfony\Bridge\Doctrine\Tests\Fixtures\CompositeIntIdEntity;
@@ -609,6 +610,40 @@ public function testAssociatedEntityWithNull()
         $this->assertNoViolation();
     }
 
+    public function testAssociatedEntityReferencedByPrimaryKey()
+    {
+        $this->registry = $this->createRegistryMock($this->em);
+        $this->registry->expects($this->any())
+            ->method('getManagerForClass')
+            ->willReturn($this->em);
+        $this->validator = $this->createValidator();
+        $this->validator->initialize($this->context);
+
+        $entity = new SingleIntIdEntity(1, 'foo');
+        $associated = new AssociationEntity();
+        $associated->single = $entity;
+
+        $this->em->persist($entity);
+        $this->em->persist($associated);
+        $this->em->flush();
+
+        $dto = new AssociatedEntityDto();
+        $dto->singleId = 1;
+
+        $this->validator->validate($dto, new UniqueEntity(
+            fields: ['singleId' => 'single'],
+            entityClass: AssociationEntity::class,
+        ));
+
+        $this->buildViolation('This value is already used.')
+            ->atPath('property.path.single')
+            ->setParameter('{{ value }}', 1)
+            ->setInvalidValue(1)
+            ->setCode(UniqueEntity::NOT_UNIQUE_ERROR)
+            ->setCause([$associated])
+            ->assertRaised();
+    }
+
     public function testValidateUniquenessWithArrayValue()
     {
         $repository = $this->createRepositoryMock(SingleIntIdEntity::class);