diff --git a/src/Symfony/Component/Form/ChoiceList/Loader/AbstractChoiceLoader.php b/src/Symfony/Component/Form/ChoiceList/Loader/AbstractChoiceLoader.php
index a98cc239f55e5..1eae069b29dcc 100644
--- a/src/Symfony/Component/Form/ChoiceList/Loader/AbstractChoiceLoader.php
+++ b/src/Symfony/Component/Form/ChoiceList/Loader/AbstractChoiceLoader.php
@@ -59,7 +59,7 @@ public function loadValuesForChoices(array $choices, callable $value = null)
 
         if ($value) {
             // if a value callback exists, use it
-            return array_map($value, $choices);
+            return array_map(function ($item) use ($value): string { return $value($item); }, $choices);
         }
 
         return $this->doLoadValuesForChoices($choices);
diff --git a/src/Symfony/Component/Form/Tests/ChoiceList/Loader/CallbackChoiceLoaderTest.php b/src/Symfony/Component/Form/Tests/ChoiceList/Loader/CallbackChoiceLoaderTest.php
index 69eb787a23dfa..40f098886b95e 100644
--- a/src/Symfony/Component/Form/Tests/ChoiceList/Loader/CallbackChoiceLoaderTest.php
+++ b/src/Symfony/Component/Form/Tests/ChoiceList/Loader/CallbackChoiceLoaderTest.php
@@ -90,6 +90,18 @@ public function testLoadChoicesForValuesLoadsChoiceListOnFirstCall()
         );
     }
 
+    public function testLoadValuesForChoicesCastsCallbackItemsToString()
+    {
+        $choices = [
+           (object) ['id' => 2],
+           (object) ['id' => 3],
+        ];
+
+        $value = function ($item) { return $item->id; };
+
+        $this->assertSame(['2', '3'], self::$loader->loadValuesForChoices($choices, $value));
+    }
+
     public function testLoadValuesForChoicesLoadsChoiceListOnFirstCall()
     {
         $this->assertSame(