diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 73f5bc7e..06731cd7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -35,7 +35,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        PHP: [ '8.1', '8.2', '8.3' ]
+        PHP: [ '8.1', '8.2', '8.3', '8.4' ]
         TYPO3: [ '^12.4', '12.4.x-dev' ]
     env:
       TYPO3_DATABASE_NAME: 'typo3_ci'
diff --git a/Classes/Process.php b/Classes/Process.php
index f167c358..bf0c3922 100644
--- a/Classes/Process.php
+++ b/Classes/Process.php
@@ -102,7 +102,7 @@ public function findPid(): ?int
         exec($ps, $output);
 
         foreach ($output as $line) {
-            [$pid, $command] = explode(' ', trim($line ?? ''), 2);
+            [$pid, $command] = explode(' ', trim($line), 2);
             $command = $this->escapePsOutputCommand($command);
             if ($command == $processCommand) {
                 return (int)$pid;
diff --git a/Classes/Report/TikaStatus.php b/Classes/Report/TikaStatus.php
index 23411b6a..0f291603 100644
--- a/Classes/Report/TikaStatus.php
+++ b/Classes/Report/TikaStatus.php
@@ -53,7 +53,7 @@ class TikaStatus implements StatusProviderInterface
      * @throws ExtensionConfigurationPathDoesNotExistException
      */
     public function __construct(
-        array $extensionConfiguration = null,
+        ?array $extensionConfiguration = null,
     ) {
         $this->tikaConfiguration = $extensionConfiguration ?? Util::getTikaExtensionConfiguration();
     }
diff --git a/Classes/Service/Extractor/AbstractExtractor.php b/Classes/Service/Extractor/AbstractExtractor.php
index a1b31df1..263760de 100644
--- a/Classes/Service/Extractor/AbstractExtractor.php
+++ b/Classes/Service/Extractor/AbstractExtractor.php
@@ -47,7 +47,7 @@ abstract class AbstractExtractor implements ExtractorInterface, LoggerAwareInter
      * @throws ExtensionConfigurationPathDoesNotExistException
      * @throws ExtensionConfigurationExtensionNotConfiguredException
      */
-    public function __construct(array $extensionConfiguration = null, SizeValidator $fileSizeValidator = null)
+    public function __construct(?array $extensionConfiguration = null, ?SizeValidator $fileSizeValidator = null)
     {
         $this->configuration = $extensionConfiguration ?? Util::getTikaExtensionConfiguration();
         $this->fileSizeValidator = $fileSizeValidator ?? GeneralUtility::makeInstance(
diff --git a/Classes/Service/File/SizeValidator.php b/Classes/Service/File/SizeValidator.php
index 905c7487..c765d1dd 100644
--- a/Classes/Service/File/SizeValidator.php
+++ b/Classes/Service/File/SizeValidator.php
@@ -35,7 +35,7 @@ class SizeValidator
      * @throws ExtensionConfigurationExtensionNotConfiguredException
      * @throws ExtensionConfigurationPathDoesNotExistException
      */
-    public function __construct(array $extensionConfiguration = null)
+    public function __construct(?array $extensionConfiguration = null)
     {
         $this->configuration = $extensionConfiguration ?? Util::getTikaExtensionConfiguration();
     }
diff --git a/Classes/Service/Tika/ServiceFactory.php b/Classes/Service/Tika/ServiceFactory.php
index 8fc4b8f6..b1a56ef6 100644
--- a/Classes/Service/Tika/ServiceFactory.php
+++ b/Classes/Service/Tika/ServiceFactory.php
@@ -39,7 +39,7 @@ class ServiceFactory
      */
     public static function getTika(
         string $tikaServiceType,
-        array $configuration = null,
+        ?array $configuration = null,
     ): ServerService|AppService|SolrCellService {
         if (empty($configuration)) {
             $configuration = Util::getTikaExtensionConfiguration();
diff --git a/Tests/Integration/Service/Tika/ServiceIntegrationTestCase.php b/Tests/Integration/Service/Tika/ServiceIntegrationTestCase.php
index ef3ec587..e7dde301 100644
--- a/Tests/Integration/Service/Tika/ServiceIntegrationTestCase.php
+++ b/Tests/Integration/Service/Tika/ServiceIntegrationTestCase.php
@@ -280,7 +280,7 @@ protected function getConfiguration(): array
 
     protected function getMockedFileInstance(
         array $fileData,
-        ResourceStorage $storage = null,
+        ?ResourceStorage $storage = null,
         array $metaData = []
     ): File|MockObject {
         $fileMock = $this->getMockBuilder(File::class)
diff --git a/Tests/Unit/ExecMockFunctions.php.Hack b/Tests/Unit/ExecMockFunctions.php.Hack
index 6e46ce8a..647376e7 100644
--- a/Tests/Unit/ExecMockFunctions.php.Hack
+++ b/Tests/Unit/ExecMockFunctions.php.Hack
@@ -29,8 +29,11 @@ use ApacheSolrForTypo3\Tika\Tests\Unit\ExecRecorder;
  * exec() mock to capture invocation parameters for the actual \exec() function
  * @noinspection PhpUnusedParameterInspection
  */
-function exec(string $command, array &$output = null, int &$result_code = null): string|false
-{
+function exec(
+    string $command,
+    ?array &$output = null,
+    ?int &$result_code = null,
+): string|false {
     $output = array_key_exists(ExecRecorder::$execCalled, ExecRecorder::$execOutput) ? ExecRecorder::$execOutput[ExecRecorder::$execCalled] : '';
     ExecRecorder::$execCalled++;
     ExecRecorder::$execCommand = $command;