diff --git a/src/Symfony/Component/ClassLoader/ClassCollectionLoader.php b/src/Symfony/Component/ClassLoader/ClassCollectionLoader.php
index 7435e3fdf4..e6fbabaab8 100644
--- a/src/Symfony/Component/ClassLoader/ClassCollectionLoader.php
+++ b/src/Symfony/Component/ClassLoader/ClassCollectionLoader.php
@@ -42,9 +42,14 @@ class ClassCollectionLoader
 
         self::$loaded[$name] = true;
 
+        $declared = array_merge(get_declared_classes(), get_declared_interfaces());
+        if (function_exists('get_declared_traits')) {
+            $declared = array_merge($declared, get_declared_traits());
+        }
+
         if ($adaptive) {
             // don't include already declared classes
-            $classes = array_diff($classes, get_declared_classes(), get_declared_interfaces());
+            $classes = array_diff($classes, $declared);
 
             // the cache is different depending on which classes are already declared
             $name = $name.'-'.substr(md5(implode('|', $classes)), 0, 5);