diff --git a/.github/workflows/php-tester-include-skipped.yml b/.github/workflows/php-tester-include-skipped.yml
index c6d72e642..ed9dcfd55 100644
--- a/.github/workflows/php-tester-include-skipped.yml
+++ b/.github/workflows/php-tester-include-skipped.yml
@@ -15,6 +15,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - uses: shivammathur/setup-php@c541c155eee45413f5b09a52248675b1a2575231 # v2
diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 534b1dd0d..1a6b41964 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -15,6 +15,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - name: OS info
       run: cat /etc/os-release
@@ -33,6 +34,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - name: Validate composer.json and composer.lock
@@ -50,6 +52,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - uses: shivammathur/setup-php@c541c155eee45413f5b09a52248675b1a2575231 # v2
@@ -70,6 +73,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - uses: shivammathur/setup-php@c541c155eee45413f5b09a52248675b1a2575231 # v2
@@ -84,6 +88,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - uses: shivammathur/setup-php@c541c155eee45413f5b09a52248675b1a2575231 # v2
@@ -98,6 +103,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - uses: shivammathur/setup-php@c541c155eee45413f5b09a52248675b1a2575231 # v2
@@ -118,6 +124,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - name: Get PHP_CodeSniffer cache file pattern
@@ -139,6 +146,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - name: Get PHPStan result cache directory
@@ -160,6 +168,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - name: Get PHPStan result cache directory
@@ -181,6 +190,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
     - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     - uses: shivammathur/setup-php@c541c155eee45413f5b09a52248675b1a2575231 # v2
@@ -223,6 +233,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - uses: shivammathur/setup-php@c541c155eee45413f5b09a52248675b1a2575231 # v2
diff --git a/.github/workflows/securitytxt.yml b/.github/workflows/securitytxt.yml
index 7345687e5..d97fc9e09 100644
--- a/.github/workflows/securitytxt.yml
+++ b/.github/workflows/securitytxt.yml
@@ -16,6 +16,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
         host:
           - www.michalspacek.cz
           - www.michalspacek.com
diff --git a/.github/workflows/tls.yml b/.github/workflows/tls.yml
index 1302d7a88..612984bfb 100644
--- a/.github/workflows/tls.yml
+++ b/.github/workflows/tls.yml
@@ -55,6 +55,7 @@ jobs:
       matrix:
         php-version:
           - "8.3"
+          - "8.4"
     steps:
       - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
       - uses: shivammathur/setup-php@c541c155eee45413f5b09a52248675b1a2575231 # v2
diff --git a/app/src/Templating/TemplateFactory.php b/app/src/Templating/TemplateFactory.php
index 88cb683c1..1b291dc78 100644
--- a/app/src/Templating/TemplateFactory.php
+++ b/app/src/Templating/TemplateFactory.php
@@ -25,7 +25,7 @@ public function __construct(
 
 
 	#[Override]
-	public function createTemplate(Control $control = null, string $class = null): DefaultTemplate
+	public function createTemplate(?Control $control = null, ?string $class = null): DefaultTemplate
 	{
 		$template = $this->templateFactory->createTemplate($control, $class);
 		if (!$template instanceof DefaultTemplate) {
diff --git a/app/src/Test/Http/Request.php b/app/src/Test/Http/Request.php
index 221ec3b6b..866b97777 100644
--- a/app/src/Test/Http/Request.php
+++ b/app/src/Test/Http/Request.php
@@ -57,14 +57,14 @@ public function setUrl(UrlScript $url): void
 
 
 	#[Override]
-	public function getQuery(string $key = null)
+	public function getQuery(?string $key = null)
 	{
 		return $key === null ? $this->url->getQueryParameters() : $this->url->getQueryParameter($key);
 	}
 
 
 	#[Override]
-	public function getPost(string $key = null)
+	public function getPost(?string $key = null)
 	{
 		return func_num_args() === 0 ? $this->post : $this->post[$key] ?? null;
 	}
diff --git a/app/src/Test/Http/Response.php b/app/src/Test/Http/Response.php
index c16a7671a..536fa6266 100644
--- a/app/src/Test/Http/Response.php
+++ b/app/src/Test/Http/Response.php
@@ -85,7 +85,7 @@ public function addHeader(string $name, string $value): self
 
 
 	#[Override]
-	public function setContentType(string $type, string $charset = null): self
+	public function setContentType(string $type, ?string $charset = null): self
 	{
 		$this->contentType = $type;
 		$this->contentCharset = $charset;
@@ -147,11 +147,11 @@ public function setCookie(
 		string $name,
 		string $value,
 		string|int|DateTimeInterface|null $expire,
-		string $path = null,
-		string $domain = null,
-		bool $secure = null,
-		bool $httpOnly = null,
-		string $sameSite = null,
+		?string $path = null,
+		?string $domain = null,
+		?bool $secure = null,
+		?bool $httpOnly = null,
+		?string $sameSite = null,
 	): self {
 		$this->cookies[$name][] = new Cookie(
 			$name,
@@ -166,7 +166,7 @@ public function setCookie(
 
 
 	#[Override]
-	public function deleteCookie(string $name, string $path = null, string $domain = null, bool $secure = null): void
+	public function deleteCookie(string $name, ?string $path = null, ?string $domain = null, ?bool $secure = null): void
 	{
 		unset($this->cookies[$name]);
 	}
diff --git a/app/src/Www/Presenters/BasePresenter.php b/app/src/Www/Presenters/BasePresenter.php
index 5a97a13a0..4c670686c 100644
--- a/app/src/Www/Presenters/BasePresenter.php
+++ b/app/src/Www/Presenters/BasePresenter.php
@@ -149,7 +149,7 @@ protected function getLocaleLinkParams(): array
 
 
 	#[Override]
-	public function lastModified(string|int|DateTimeInterface|null $lastModified, string $etag = null, string $expire = null): void
+	public function lastModified(string|int|DateTimeInterface|null $lastModified, ?string $etag = null, ?string $expire = null): void
 	{
 		$compression = ini_get('zlib.output_compression');
 		ini_set('zlib.output_compression', false);
diff --git a/app/tests/Training/Files/TrainingFilesDownloadTest.phpt b/app/tests/Training/Files/TrainingFilesDownloadTest.phpt
index 9838417a8..c7a73da40 100644
--- a/app/tests/Training/Files/TrainingFilesDownloadTest.phpt
+++ b/app/tests/Training/Files/TrainingFilesDownloadTest.phpt
@@ -113,7 +113,7 @@ class TrainingFilesDownloadTest extends TestCase
 		$sessionSection = $this->session->getSection('training');
 		$sessionSection->set('applicationId', self::APPLICATION_ID);
 		$sessionSection->set('token', self::TOKEN);
-		$filename = basename(__FILE__);
+		$filename = 'file.zip';
 		$filesDir = __DIR__ . '/';
 		$this->database->setFetchResult([
 			'added' => new DateTime(),
@@ -125,7 +125,7 @@ class TrainingFilesDownloadTest extends TestCase
 		$response = $this->trainingFilesDownload->getFileResponse('foo');
 		Assert::same($filesDir . $filename, $response->getFile());
 		Assert::same($filename, $response->getName());
-		Assert::same('text/x-php', $response->getContentType());
+		Assert::same('application/zip', $response->getContentType());
 	}
 
 
diff --git a/app/tests/Training/Files/file.zip b/app/tests/Training/Files/file.zip
new file mode 100644
index 000000000..15cb0ecb3
Binary files /dev/null and b/app/tests/Training/Files/file.zip differ