diff --git a/.github/workflows/Build.yml b/.github/workflows/Build.yml
index b89df2b..f751ad8 100644
--- a/.github/workflows/Build.yml
+++ b/.github/workflows/Build.yml
@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php_versions: ['8.1', '8.2', '8.3']
+        php_versions: ['8.1', '8.2', '8.3', '8.4']
         os: [ubuntu-latest, windows-latest]
 
     runs-on: ${{ matrix.os }}
diff --git a/.github/workflows/PHPStan.yml b/.github/workflows/PHPStan.yml
index e0a0e1d..42e3778 100644
--- a/.github/workflows/PHPStan.yml
+++ b/.github/workflows/PHPStan.yml
@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php_versions: ['8.1', '8.2', '8.3']
+        php_versions: ['8.1', '8.2', '8.3', '8.4']
 
     runs-on: ubuntu-latest
     name: PHPStan - ${{ matrix.php_versions }}
diff --git a/src/Fortress/ServerSideValidator.php b/src/Fortress/ServerSideValidator.php
index bc1458a..e77f44e 100644
--- a/src/Fortress/ServerSideValidator.php
+++ b/src/Fortress/ServerSideValidator.php
@@ -86,7 +86,7 @@ public function data(): array
      *
      * @return mixed[]|bool
      */
-    public function errors(string $field = null)
+    public function errors(string|null $field = null)
     {
         if ($field !== null) {
             return isset($this->errors[$field]) ? $this->errors[$field] : false;