diff --git a/tests/ACL/ACLCacheWrapperTest.php b/tests/ACL/ACLCacheWrapperTest.php
index 8e840f3..1588428 100644
--- a/tests/ACL/ACLCacheWrapperTest.php
+++ b/tests/ACL/ACLCacheWrapperTest.php
@@ -38,7 +38,7 @@ class ACLCacheWrapperTest extends TestCase {
 	private $cache;
 	private $aclPermissions = [];
 
-	protected function setUp() {
+	protected function setUp(): void {
 		parent::setUp();
 
 		$this->aclManager = $this->createMock(ACLManager::class);
diff --git a/tests/ACL/ACLManagerTest.php b/tests/ACL/ACLManagerTest.php
index 6fc5d92..cf0c484 100644
--- a/tests/ACL/ACLManagerTest.php
+++ b/tests/ACL/ACLManagerTest.php
@@ -44,7 +44,7 @@ class ACLManagerTest extends TestCase {
 	/** @var Rule[] */
 	private $rules = [];
 
-	protected function setUp() {
+	protected function setUp(): void {
 		parent::setUp();
 
 		$this->user = $this->createMock(IUser::class);
diff --git a/tests/ACL/ACLStorageWrapperTest.php b/tests/ACL/ACLStorageWrapperTest.php
index 976fdda..80f2e3d 100644
--- a/tests/ACL/ACLStorageWrapperTest.php
+++ b/tests/ACL/ACLStorageWrapperTest.php
@@ -37,7 +37,7 @@ class ACLStorageWrapperTest extends TestCase {
 	private $storage;
 	private $aclPermissions = [];
 
-	protected function setUp() {
+	protected function setUp(): void {
 		parent::setUp();
 
 		$this->aclManager = $this->createMock(ACLManager::class);
diff --git a/tests/ACL/RuleManagerTest.php b/tests/ACL/RuleManagerTest.php
index b4941ba..e76b1bd 100644
--- a/tests/ACL/RuleManagerTest.php
+++ b/tests/ACL/RuleManagerTest.php
@@ -40,7 +40,7 @@ class RuleManagerTest extends TestCase {
 	/** @var \PHPUnit_Framework_MockObject_MockObject | IUser */
 	private $user;
 
-	protected function setUp() {
+	protected function setUp(): void {
 		parent::setUp();
 
 		$this->user = $this->createMock(IUser::class);
diff --git a/tests/Folder/FolderManagerTest.php b/tests/Folder/FolderManagerTest.php
index 6a53d7b..386b575 100644
--- a/tests/Folder/FolderManagerTest.php
+++ b/tests/Folder/FolderManagerTest.php
@@ -41,7 +41,7 @@ class FolderManagerTest extends TestCase {
 	/** @var IMimeTypeLoader */
 	private $mimeLoader;
 
-	protected function setUp() {
+	protected function setUp(): void {
 		parent::setUp();
 
 		$this->groupManager = $this->createMock(IGroupManager::class);