diff --git a/src/ControllerMethodParameter.php b/src/ControllerMethodParameter.php
index 5bf2c2c..bb15da5 100644
--- a/src/ControllerMethodParameter.php
+++ b/src/ControllerMethodParameter.php
@@ -1,10 +1,11 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * SPDX-FileCopyrightText: 2023 Nextcloud GmbH and Nextcloud contributors
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
-
 namespace OpenAPIExtractor;
 
 class ControllerMethodParameter {
diff --git a/src/ControllerMethodResponse.php b/src/ControllerMethodResponse.php
index c5ae828..7558037 100644
--- a/src/ControllerMethodResponse.php
+++ b/src/ControllerMethodResponse.php
@@ -1,10 +1,11 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * SPDX-FileCopyrightText: 2023 Nextcloud GmbH and Nextcloud contributors
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
-
 namespace OpenAPIExtractor;
 
 class ControllerMethodResponse {
diff --git a/src/Logger.php b/src/Logger.php
index cd15db2..451bf60 100644
--- a/src/Logger.php
+++ b/src/Logger.php
@@ -1,10 +1,11 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * SPDX-FileCopyrightText: 2023 Nextcloud GmbH and Nextcloud contributors
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
-
 namespace OpenAPIExtractor;
 
 class Logger {
diff --git a/src/LoggerLevel.php b/src/LoggerLevel.php
index de2687e..e702606 100644
--- a/src/LoggerLevel.php
+++ b/src/LoggerLevel.php
@@ -1,10 +1,11 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * SPDX-FileCopyrightText: 2023 Nextcloud GmbH and Nextcloud contributors
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
-
 namespace OpenAPIExtractor;
 
 enum LoggerLevel: string {
diff --git a/src/UnsupportedExprException.php b/src/UnsupportedExprException.php
index 76637c9..9071222 100644
--- a/src/UnsupportedExprException.php
+++ b/src/UnsupportedExprException.php
@@ -1,10 +1,11 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * SPDX-FileCopyrightText: 2024 Nextcloud GmbH and Nextcloud contributors
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
-
 namespace OpenAPIExtractor;
 
 use Exception;
diff --git a/tests/lib/Controller/AdminSettingsController.php b/tests/lib/Controller/AdminSettingsController.php
index 4f769b5..c8e2aa1 100644
--- a/tests/lib/Controller/AdminSettingsController.php
+++ b/tests/lib/Controller/AdminSettingsController.php
@@ -77,7 +77,7 @@ public function movedToSettingsTagUnnamed(): DataResponse {
 	public function optionalParameters(
 		int $option1 = 0,
 		int $option2 = self::ALSO_OPTIONAL,
-	) {
+	): \OCP\AppFramework\Http\DataResponse {
 		return new DataResponse();
 	}
 
diff --git a/tests/lib/Controller/RoutingController.php b/tests/lib/Controller/RoutingController.php
index 96c81e4..a2c3291 100644
--- a/tests/lib/Controller/RoutingController.php
+++ b/tests/lib/Controller/RoutingController.php
@@ -22,7 +22,7 @@ class RoutingController extends OCSController {
 	 */
 	#[Route(Route::TYPE_API, verb: 'GET', url: '/attribute-ocs/{param}', requirements: ['param' => '[a-z]+'], defaults: ['param' => 'abc'], root: '/tests', postfix: 'Route')]
 	#[ApiRoute(verb: 'POST', url: '/attribute-ocs/{param}', requirements: ['param' => '[a-z]+'], defaults: ['param' => 'abc'], root: '/tests', postfix: 'ApiRoute')]
-	public function attributeOCS() {
+	public function attributeOCS(): \OCP\AppFramework\Http\DataResponse {
 		return new DataResponse();
 	}
 
@@ -36,7 +36,7 @@ public function attributeOCS() {
 	 */
 	#[Route(Route::TYPE_FRONTPAGE, verb: 'GET', url: '/attribute-index/{param}', requirements: ['param' => '[a-z]+'], defaults: ['param' => 'abc'], root: '/tests', postfix: 'Route')]
 	#[FrontpageRoute(verb: 'POST', url: '/attribute-index/{param}', requirements: ['param' => '[a-z]+'], defaults: ['param' => 'abc'], root: '/tests', postfix: 'FrontpageRoute')]
-	public function attributeIndex() {
+	public function attributeIndex(): \OCP\AppFramework\Http\DataResponse {
 		return new DataResponse();
 	}
 
@@ -47,7 +47,7 @@ public function attributeIndex() {
 	 * 200: Success
 	 */
 	#[FrontpageRoute(verb: 'PUT', url: '/attribute-index/{param}', requirements: ['param' => '[a-z]+'], defaults: ['param' => 'abc'], root: '/tests')]
-	public function csrfIndex() {
+	public function csrfIndex(): \OCP\AppFramework\Http\DataResponse {
 		return new DataResponse();
 	}
 }