diff --git a/src/Frontend/Assets/LibrariesConfiguration.php b/src/Frontend/Assets/LibrariesConfiguration.php
index 54929d8..c095c32 100644
--- a/src/Frontend/Assets/LibrariesConfiguration.php
+++ b/src/Frontend/Assets/LibrariesConfiguration.php
@@ -5,7 +5,8 @@
  *
  * @package    contao-leaflet-maps
  * @author     David Molineus <david.molineus@netzmacht.de>
- * @copyright  2014-2017 netzmacht David Molineus. All rights reserved.
+ * @author     Sven Baumnn <baumann.sv@gmail.com>
+ * @copyright  2014-2022 netzmacht David Molineus. All rights reserved.
  * @license    LGPL-3.0 https://github.com/netzmacht/contao-leaflet-maps/blob/master/LICENSE
  * @filesource
  */
@@ -15,6 +16,7 @@ declare(strict_types=1);
 namespace Netzmacht\Contao\Leaflet\Frontend\Assets;
 
 use Contao\CoreBundle\Framework\ContaoFrameworkInterface as ContaoFramework;
+use Traversable;
 
 /**
  * Class LibrariesConfiguration.
@@ -45,7 +47,7 @@ class LibrariesConfiguration implements \IteratorAggregate, \ArrayAccess
      *
      * @SuppressWarnings(PHPMD.Superglobals)
      */
-    public function getIterator()
+    public function getIterator(): Traversable
     {
         $this->framework->initialize();
 
@@ -57,7 +59,7 @@ class LibrariesConfiguration implements \IteratorAggregate, \ArrayAccess
      *
      * @SuppressWarnings(PHPMD.Superglobals)
      */
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         $this->framework->initialize();
 
@@ -81,7 +83,7 @@ class LibrariesConfiguration implements \IteratorAggregate, \ArrayAccess
      *
      * @SuppressWarnings(PHPMD.Superglobals)
      */
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
         $this->framework->initialize();
 
@@ -93,7 +95,7 @@ class LibrariesConfiguration implements \IteratorAggregate, \ArrayAccess
      *
      * @SuppressWarnings(PHPMD.Superglobals)
      */
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
         $this->framework->initialize();