diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 2025ae2..7b729a7 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-versions: [ '8.3' ]
+        php-versions: ['8.3', '8.4']
         dependency-versions: [ 'highest', 'lowest' ]
     runs-on: ubuntu-latest
     steps:
diff --git a/src/Test/ConstraintValidatorTestCase.php b/src/Test/ConstraintValidatorTestCase.php
index 23c6bff..ef70c37 100644
--- a/src/Test/ConstraintValidatorTestCase.php
+++ b/src/Test/ConstraintValidatorTestCase.php
@@ -54,7 +54,7 @@ abstract public function providerValidValues(): iterable;
      * @dataProvider providerInvalidValues
      * @param array<string, mixed>|null $parameters
      */
-    public function testInvalidValues(mixed $value, string $code, string $message, array $parameters = null): void
+    public function testInvalidValues(mixed $value, string $code, string $message, ?array $parameters = null): void
     {
         $this->validator->validate($value, $this->getConstraint());
         $this->buildViolation($message)