diff --git a/concrete/src/Url/Resolver/Manager/ResolverManager.php b/concrete/src/Url/Resolver/Manager/ResolverManager.php
index <HASH>..<HASH> 100644
--- a/concrete/src/Url/Resolver/Manager/ResolverManager.php
+++ b/concrete/src/Url/Resolver/Manager/ResolverManager.php
@@ -23,6 +23,7 @@ class ResolverManager implements ResolverManagerInterface
      */
     public function __construct($default_handle = '', UrlResolverInterface $default_resolver = null)
     {
+        $this->priorityTree = [];
         if ($default_resolver) {
             $this->addResolver($default_handle, $default_resolver);
         }
Initialize ResolverManager::priorityTree

Otherwise we risk to iterate on null