diff --git a/Legacy/SymfonyTestsListenerTrait.php b/Legacy/SymfonyTestsListenerTrait.php
index 6333c4fd..2c7391a0 100644
--- a/Legacy/SymfonyTestsListenerTrait.php
+++ b/Legacy/SymfonyTestsListenerTrait.php
@@ -83,6 +83,16 @@ public function __construct(array $mockedNamespaces = array())
         }
     }
 
+    public function __sleep()
+    {
+        throw new \BadMethodCallException('Cannot serialize '.__CLASS__);
+    }
+
+    public function __wakeup()
+    {
+        throw new \BadMethodCallException('Cannot unserialize '.__CLASS__);
+    }
+
     public function __destruct()
     {
         if (0 < $this->state) {