diff --git a/src/Core/Cache/CacheDriverFactory.php b/src/Core/Cache/CacheDriverFactory.php
index d15b8e9858..e9ff4331d7 100644
--- a/src/Core/Cache/CacheDriverFactory.php
+++ b/src/Core/Cache/CacheDriverFactory.php
@@ -20,7 +20,7 @@ class CacheDriverFactory
 	 * @return ICacheDriver  The instance of the CacheDriver
 	 * @throws \Exception    The exception if something went wrong during the CacheDriver creation
 	 */
-	public static function create(string $driver) : ICacheDriver {
+	public static function create(string $driver) {
 
 		switch ($driver) {
 			case 'memcache':
diff --git a/src/Core/Lock/AbstractLockDriver.php b/src/Core/Lock/AbstractLockDriver.php
index 15820c3782..4c2bfaec95 100644
--- a/src/Core/Lock/AbstractLockDriver.php
+++ b/src/Core/Lock/AbstractLockDriver.php
@@ -22,7 +22,7 @@ abstract class AbstractLockDriver implements ILockDriver
 	 * @param string key The Name of the lock
 	 * @return bool      Returns true if the lock is set
 	 */
-	protected function hasAcquiredLock(string $key): bool {
+	protected function hasAcquiredLock(string $key) {
 		return isset($this->acquireLock[$key]);
 	}
 
diff --git a/src/Core/Lock/SemaphoreLockDriver.php b/src/Core/Lock/SemaphoreLockDriver.php
index 84965a1643..4eb30b9d02 100644
--- a/src/Core/Lock/SemaphoreLockDriver.php
+++ b/src/Core/Lock/SemaphoreLockDriver.php
@@ -18,7 +18,7 @@ class SemaphoreLockDriver extends AbstractLockDriver
 	 *
 	 * @return integer the semaphore key
 	 */
-	private static function semaphoreKey(string $key): int
+	private static function semaphoreKey(string $key)
 	{
 		$temp = get_temppath();