diff --git a/src/Symfony/Component/Cache/Traits/PhpFilesTrait.php b/src/Symfony/Component/Cache/Traits/PhpFilesTrait.php
index b57addb54fb1..37d25f87a98f 100644
--- a/src/Symfony/Component/Cache/Traits/PhpFilesTrait.php
+++ b/src/Symfony/Component/Cache/Traits/PhpFilesTrait.php
@@ -133,7 +133,7 @@ protected function doFetch(array $ids)
      */
     protected function doHave($id)
     {
-        if ($this->appendOnly && $this->values[$id]) {
+        if ($this->appendOnly && isset($this->values[$id])) {
             return true;
         }