diff --git a/src/Security/UserClassBuilder.php b/src/Security/UserClassBuilder.php
index 8a1e9fa09..261780368 100644
--- a/src/Security/UserClassBuilder.php
+++ b/src/Security/UserClassBuilder.php
@@ -12,6 +12,7 @@
 namespace Symfony\Bundle\MakerBundle\Security;
 
 use PhpParser\Node;
+use Symfony\Bundle\MakerBundle\Str;
 use Symfony\Bundle\MakerBundle\Util\ClassSource\Model\ClassProperty;
 use Symfony\Bundle\MakerBundle\Util\ClassSourceManipulator;
 use Symfony\Component\Security\Core\User\PasswordAuthenticatedUserInterface;
@@ -28,6 +29,8 @@ public function addUserInterfaceImplementation(ClassSourceManipulator $manipulat
     {
         $manipulator->addInterface(UserInterface::class);
 
+        $this->addUniqueConstraint($manipulator, $userClassConfig);
+
         $this->addGetUsername($manipulator, $userClassConfig);
 
         $this->addGetRoles($manipulator, $userClassConfig);
@@ -57,7 +60,6 @@ private function addGetUsername(ClassSourceManipulator $manipulator, UserClassCo
                     propertyName: $userClassConfig->getIdentityPropertyName(),
                     type: 'string',
                     length: 180,
-                    unique: true,
                 )
             );
         } else {
@@ -259,4 +261,19 @@ private function addEraseCredentials(ClassSourceManipulator $manipulator): void
 
         $manipulator->addMethodBuilder($builder);
     }
+
+    private function addUniqueConstraint(ClassSourceManipulator $manipulator, UserClassConfiguration $userClassConfig): void
+    {
+        if (!$userClassConfig->isEntity()) {
+            return;
+        }
+
+        $manipulator->addAttributeToClass(
+            'ORM\\UniqueConstraint',
+            [
+                'name' => 'UNIQ_IDENTIFIER_'.strtoupper(Str::asSnakeCase($userClassConfig->getIdentityPropertyName())),
+                'fields' => [$userClassConfig->getIdentityPropertyName()],
+            ]
+        );
+    }
 }
diff --git a/src/Util/ClassSourceManipulator.php b/src/Util/ClassSourceManipulator.php
index 4dbe9c05d..cde3cade1 100644
--- a/src/Util/ClassSourceManipulator.php
+++ b/src/Util/ClassSourceManipulator.php
@@ -395,7 +395,9 @@ public function addAttributeToClass(string $attributeClass, array $options): voi
 
         $classNode = $this->getClassNode();
 
-        $classNode->attrGroups[] = new Node\AttributeGroup([$this->buildAttributeNode($attributeClass, $options)]);
+        $attributePrefix = str_starts_with($attributeClass, 'ORM\\') ? 'ORM' : null;
+
+        $classNode->attrGroups[] = new Node\AttributeGroup([$this->buildAttributeNode($attributeClass, $options, $attributePrefix)]);
 
         $this->updateSourceCodeFromNewStmts();
     }
@@ -783,6 +785,10 @@ public function addUseStatementIfNecessary(string $class): string
                         return $alias;
                     }
 
+                    if (str_starts_with($class, $alias)) {
+                        return $class;
+                    }
+
                     if ($alias === $shortClassName) {
                         // we have a conflicting alias!
                         // to be safe, use the fully-qualified class name
diff --git a/tests/Security/fixtures/expected/UserEntityWithEmailAsIdentifier.php b/tests/Security/fixtures/expected/UserEntityWithEmailAsIdentifier.php
index 722dd2507..71d2e49fa 100644
--- a/tests/Security/fixtures/expected/UserEntityWithEmailAsIdentifier.php
+++ b/tests/Security/fixtures/expected/UserEntityWithEmailAsIdentifier.php
@@ -7,6 +7,7 @@
 use Symfony\Component\Security\Core\User\UserInterface;
 
 #[ORM\Entity]
+#[ORM\UniqueConstraint(name: 'UNIQ_IDENTIFIER_EMAIL', fields: ['email'])]
 class User implements UserInterface, PasswordAuthenticatedUserInterface
 {
     #[ORM\Id]
@@ -14,7 +15,7 @@ class User implements UserInterface, PasswordAuthenticatedUserInterface
     #[ORM\Column()]
     private ?int $id = null;
 
-    #[ORM\Column(length: 180, unique: true)]
+    #[ORM\Column(length: 180)]
     private ?string $email = null;
 
     /**
diff --git a/tests/Security/fixtures/expected/UserEntityWithPassword.php b/tests/Security/fixtures/expected/UserEntityWithPassword.php
index c2a0ca349..dc4999299 100644
--- a/tests/Security/fixtures/expected/UserEntityWithPassword.php
+++ b/tests/Security/fixtures/expected/UserEntityWithPassword.php
@@ -7,6 +7,7 @@
 use Symfony\Component\Security\Core\User\UserInterface;
 
 #[ORM\Entity]
+#[ORM\UniqueConstraint(name: 'UNIQ_IDENTIFIER_USER_IDENTIFIER', fields: ['userIdentifier'])]
 class User implements UserInterface, PasswordAuthenticatedUserInterface
 {
     #[ORM\Id]
@@ -14,7 +15,7 @@ class User implements UserInterface, PasswordAuthenticatedUserInterface
     #[ORM\Column()]
     private ?int $id = null;
 
-    #[ORM\Column(length: 180, unique: true)]
+    #[ORM\Column(length: 180)]
     private ?string $userIdentifier = null;
 
     /**
diff --git a/tests/Security/fixtures/expected/UserEntityWithUser_IdentifierAsIdentifier.php b/tests/Security/fixtures/expected/UserEntityWithUser_IdentifierAsIdentifier.php
index ae8333885..a77a08fed 100644
--- a/tests/Security/fixtures/expected/UserEntityWithUser_IdentifierAsIdentifier.php
+++ b/tests/Security/fixtures/expected/UserEntityWithUser_IdentifierAsIdentifier.php
@@ -7,6 +7,7 @@
 use Symfony\Component\Security\Core\User\UserInterface;
 
 #[ORM\Entity]
+#[ORM\UniqueConstraint(name: 'UNIQ_IDENTIFIER_USER_IDENTIFIER', fields: ['user_identifier'])]
 class User implements UserInterface, PasswordAuthenticatedUserInterface
 {
     #[ORM\Id]
@@ -14,7 +15,7 @@ class User implements UserInterface, PasswordAuthenticatedUserInterface
     #[ORM\Column()]
     private ?int $id = null;
 
-    #[ORM\Column(length: 180, unique: true)]
+    #[ORM\Column(length: 180)]
     private ?string $user_identifier = null;
 
     /**
diff --git a/tests/Security/fixtures/expected/UserEntityWithoutPassword.php b/tests/Security/fixtures/expected/UserEntityWithoutPassword.php
index bd90ddb36..a1deca0f6 100644
--- a/tests/Security/fixtures/expected/UserEntityWithoutPassword.php
+++ b/tests/Security/fixtures/expected/UserEntityWithoutPassword.php
@@ -6,6 +6,7 @@
 use Symfony\Component\Security\Core\User\UserInterface;
 
 #[ORM\Entity]
+#[ORM\UniqueConstraint(name: 'UNIQ_IDENTIFIER_USER_IDENTIFIER', fields: ['userIdentifier'])]
 class User implements UserInterface
 {
     #[ORM\Id]
@@ -13,7 +14,7 @@ class User implements UserInterface
     #[ORM\Column()]
     private ?int $id = null;
 
-    #[ORM\Column(length: 180, unique: true)]
+    #[ORM\Column(length: 180)]
     private ?string $userIdentifier = null;
 
     /**