diff --git a/src/Pho/Framework/Actor.php b/src/Pho/Framework/Actor.php
index 9511606..00dcb5f 100644
--- a/src/Pho/Framework/Actor.php
+++ b/src/Pho/Framework/Actor.php
@@ -46,7 +46,7 @@ class Actor extends \Pho\Lib\Graph\Node implements ParticleInterface {
     public function __construct(ContextInterface $context) {
         parent::__construct($context);
         $this->creator = $this;
-        $this->creator_id = $this->id();
+        $this->creator_id = (string) $this->id();
         $this->enter($context);
         $this->setupEdges();
     }
diff --git a/src/Pho/Framework/Frame.php b/src/Pho/Framework/Frame.php
index 1a7c8fe..221c018 100644
--- a/src/Pho/Framework/Frame.php
+++ b/src/Pho/Framework/Frame.php
@@ -45,7 +45,7 @@ class Frame extends \Pho\Lib\Graph\SubGraph implements ParticleInterface, Contex
     public function __construct(Actor $creator, ContextInterface $context) {
         parent::__construct($context);
         $this->creator = $creator;
-        $this->creator_id = $creator->id();
+        $this->creator_id = (string) $creator->id();
         $this->setupEdges();
     }
 
diff --git a/src/Pho/Framework/Object.php b/src/Pho/Framework/Object.php
index 3bc92da..c7e5a03 100644
--- a/src/Pho/Framework/Object.php
+++ b/src/Pho/Framework/Object.php
@@ -37,7 +37,7 @@ class Object extends \Pho\Lib\Graph\Node implements ParticleInterface {
     public function __construct(Actor $creator, ContextInterface $context) {
         parent::__construct($context);
         $this->creator = $creator;
-        $this->creator_id = $creator->id();
+        $this->creator_id = (string) $creator->id();
         $this->setupEdges();
     }