diff --git a/src/Traits/ModelTree.php b/src/Traits/ModelTree.php
index 128237e..e576d22 100755
--- a/src/Traits/ModelTree.php
+++ b/src/Traits/ModelTree.php
@@ -97,7 +97,7 @@ trait ModelTree
      *
      * @return array
      */
-    public function toTree(array $nodes = null)
+    public function toTree($nodes = null)
     {
         if ($nodes === null) {
             $nodes = $this->allNodes();