diff --git a/library/HTMLPurifier/DefinitionCache/Serializer.php b/library/HTMLPurifier/DefinitionCache/Serializer.php
index bfad967f..6ba9ad2d 100644
--- a/library/HTMLPurifier/DefinitionCache/Serializer.php
+++ b/library/HTMLPurifier/DefinitionCache/Serializer.php
@@ -139,8 +139,9 @@ class HTMLPurifier_DefinitionCache_Serializer extends HTMLPurifier_DefinitionCac
                 continue;
             }
             $key = substr($filename, 0, strlen($filename) - 4);
-            if ($this->isOld($key, $config)) {
-                unlink($dir . '/' . $filename);
+            $file = $dir . '/' . $filename;
+            if ($this->isOld($key, $config) && file_exists($file)) {
+                unlink($file);
             }
         }
         closedir($dh);