diff --git a/src/Caching/ProxyCacheFactory.php b/src/Caching/ProxyCacheFactory.php
index c87d5374..f222af4a 100644
--- a/src/Caching/ProxyCacheFactory.php
+++ b/src/Caching/ProxyCacheFactory.php
@@ -20,7 +20,7 @@ class ProxyCacheFactory extends DefaultCacheFactory
      */
     protected $containerClass = null;
 
-    public function create($service, array $args = [])
+    public function create(string $service, array $args = []): CacheInterface
     {
         $backend = parent::create($service, $args);