diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9ec062c..1505d22 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,6 +18,8 @@ jobs:
                     - php: '7.4'
                       deps: lowest
                       deprecations: max[self]=0
+                    - php: '8.0'
+                      deps: highest
 
         steps:
             - name: Checkout code
@@ -29,6 +31,10 @@ jobs:
                   php-version: '${{ matrix.php }}'
                   coverage: none
 
+            - name: Configure composer
+              if: "${{ matrix.deps == 'highest' }}"
+              run: composer config minimum-stability dev
+
             - name: Composer install
               uses: ramsey/composer-install@v1
               with:
diff --git a/Domain/UserSecurityIdentity.php b/Domain/UserSecurityIdentity.php
index 50796b5..7f3ca7f 100644
--- a/Domain/UserSecurityIdentity.php
+++ b/Domain/UserSecurityIdentity.php
@@ -54,7 +54,7 @@ public function __construct($username, $class)
      */
     public static function fromAccount(UserInterface $user)
     {
-        return new self($user->getUsername(), ClassUtils::getRealClass($user));
+        return new self(method_exists($user, 'getUserIdentifier') ? $user->getUserIdentifier() : $user->getUsername(), ClassUtils::getRealClass($user));
     }
 
     /**
diff --git a/Tests/Domain/SecurityIdentityRetrievalStrategyTest.php b/Tests/Domain/SecurityIdentityRetrievalStrategyTest.php
index 88b2afe..81e3ef8 100644
--- a/Tests/Domain/SecurityIdentityRetrievalStrategyTest.php
+++ b/Tests/Domain/SecurityIdentityRetrievalStrategyTest.php
@@ -16,11 +16,11 @@
 use Symfony\Component\Security\Acl\Domain\RoleSecurityIdentity;
 use Symfony\Component\Security\Acl\Domain\SecurityIdentityRetrievalStrategy;
 use Symfony\Component\Security\Acl\Domain\UserSecurityIdentity;
+use Symfony\Component\Security\Acl\Tests\Fixtures\Account;
 use Symfony\Component\Security\Core\Authentication\AuthenticationTrustResolverInterface;
 use Symfony\Component\Security\Core\Authentication\Token\AbstractToken;
 use Symfony\Component\Security\Core\Authentication\Token\AnonymousToken;
 use Symfony\Component\Security\Core\Role\RoleHierarchyInterface;
-use Symfony\Component\Security\Core\User\UserInterface;
 
 class SecurityIdentityRetrievalStrategyTest extends TestCase
 {
@@ -81,8 +81,8 @@ public function testGetSecurityIdentities($user, array $roles, string $authentic
     public function getSecurityIdentityRetrievalTests(): array
     {
         return [
-            [$this->getAccount('johannes', 'FooUser'), ['ROLE_USER', 'ROLE_SUPERADMIN'], 'fullFledged', [
-                new UserSecurityIdentity('johannes', 'FooUser'),
+            [new Account('johannes'), ['ROLE_USER', 'ROLE_SUPERADMIN'], 'fullFledged', [
+                new UserSecurityIdentity('johannes', Account::class),
                 new RoleSecurityIdentity('ROLE_USER'),
                 new RoleSecurityIdentity('ROLE_SUPERADMIN'),
                 new RoleSecurityIdentity('IS_AUTHENTICATED_FULLY'),
@@ -103,8 +103,8 @@ public function getSecurityIdentityRetrievalTests(): array
                 new RoleSecurityIdentity('IS_AUTHENTICATED_REMEMBERED'),
                 new RoleSecurityIdentity('IS_AUTHENTICATED_ANONYMOUSLY'),
             ]],
-            [$this->getAccount('foo', 'FooBarUser'), ['ROLE_FOO'], 'rememberMe', [
-                new UserSecurityIdentity('foo', 'FooBarUser'),
+            [new Account('foo'), ['ROLE_FOO'], 'rememberMe', [
+                new UserSecurityIdentity('foo', Account::class),
                 new RoleSecurityIdentity('ROLE_FOO'),
                 new RoleSecurityIdentity('IS_AUTHENTICATED_REMEMBERED'),
                 new RoleSecurityIdentity('IS_AUTHENTICATED_ANONYMOUSLY'),
@@ -116,21 +116,6 @@ public function getSecurityIdentityRetrievalTests(): array
         ];
     }
 
-    private function getAccount(string $username, string $class): UserInterface
-    {
-        $account = $this->getMockBuilder(UserInterface::class)
-            ->setMockClassName($class)
-            ->getMock()
-        ;
-        $account
-            ->expects($this->any())
-            ->method('getUsername')
-            ->willReturn($username)
-        ;
-
-        return $account;
-    }
-
     private function getStrategy(array $roles, string $authenticationStatus): SecurityIdentityRetrievalStrategy
     {
         $roleHierarchy = new class($roles) implements RoleHierarchyInterface {
diff --git a/Tests/Domain/UserSecurityIdentityTest.php b/Tests/Domain/UserSecurityIdentityTest.php
index b014620..602a78b 100644
--- a/Tests/Domain/UserSecurityIdentityTest.php
+++ b/Tests/Domain/UserSecurityIdentityTest.php
@@ -13,6 +13,9 @@
 
 use Symfony\Component\Security\Acl\Domain\RoleSecurityIdentity;
 use Symfony\Component\Security\Acl\Domain\UserSecurityIdentity;
+use Symfony\Component\Security\Acl\Model\SecurityIdentityInterface;
+use Symfony\Component\Security\Acl\Tests\Fixtures\Account;
+use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
 
 class UserSecurityIdentityTest extends \PHPUnit\Framework\TestCase
 {
@@ -36,23 +39,16 @@ public function testConstructorWithProxy()
     /**
      * @dataProvider getCompareData
      */
-    public function testEquals($id1, $id2, $equal)
+    public function testEquals(UserSecurityIdentity $id1, SecurityIdentityInterface $id2, bool $equal)
     {
         $this->assertSame($equal, $id1->equals($id2));
     }
 
-    public function getCompareData()
+    public function getCompareData(): array
     {
-        $account = $this->getMockBuilder('Symfony\Component\Security\Core\User\UserInterface')
-                            ->setMockClassName('USI_AccountImpl')
-                            ->getMock();
-        $account
-            ->expects($this->any())
-            ->method('getUsername')
-            ->willReturn('foo')
-        ;
+        $account = new Account('foo');
 
-        $token = $this->createMock('Symfony\Component\Security\Core\Authentication\Token\TokenInterface');
+        $token = $this->createMock(TokenInterface::class);
         $token
             ->expects($this->any())
             ->method('getUser')
@@ -67,7 +63,7 @@ public function getCompareData()
             [new UserSecurityIdentity('bla', 'Foo'), new UserSecurityIdentity('blub', 'Foo'), false],
             [new UserSecurityIdentity('foo', 'Foo'), new RoleSecurityIdentity('foo'), false],
             [new UserSecurityIdentity('foo', 'Foo'), UserSecurityIdentity::fromToken($token), false],
-            [new UserSecurityIdentity('foo', 'USI_AccountImpl'), UserSecurityIdentity::fromToken($token), true],
+            [new UserSecurityIdentity('foo', Account::class), UserSecurityIdentity::fromToken($token), true],
         ];
     }
 }
diff --git a/Tests/Fixtures/Account.php b/Tests/Fixtures/Account.php
new file mode 100644
index 0000000..373b1d3
--- /dev/null
+++ b/Tests/Fixtures/Account.php
@@ -0,0 +1,45 @@
+<?php
+
+namespace Symfony\Component\Security\Acl\Tests\Fixtures;
+
+use Symfony\Component\Security\Core\User\UserInterface;
+
+final class Account implements UserInterface
+{
+    /** @var string */
+    private $identifier;
+
+    public function __construct(string $identifier)
+    {
+        $this->identifier = $identifier;
+    }
+
+    public function getUserIdentifier(): string
+    {
+        return $this->identifier;
+    }
+
+    public function getUsername(): string
+    {
+        return $this->getUserIdentifier();
+    }
+
+    public function getRoles(): array
+    {
+        return ['ROLE_USER'];
+    }
+
+    public function getPassword(): ?string
+    {
+        return null;
+    }
+
+    public function getSalt(): ?string
+    {
+        return null;
+    }
+
+    public function eraseCredentials(): void
+    {
+    }
+}