diff --git a/library/HTMLPurifier/DefinitionCache/Serializer.php b/library/HTMLPurifier/DefinitionCache/Serializer.php
index 7fb106f3..952e48d4 100644
--- a/library/HTMLPurifier/DefinitionCache/Serializer.php
+++ b/library/HTMLPurifier/DefinitionCache/Serializer.php
@@ -112,6 +112,7 @@ class HTMLPurifier_DefinitionCache_Serializer extends HTMLPurifier_DefinitionCac
             }
             unlink($dir . '/' . $filename);
         }
+        closedir($dh);
         return true;
     }
 
@@ -142,6 +143,7 @@ class HTMLPurifier_DefinitionCache_Serializer extends HTMLPurifier_DefinitionCac
                 unlink($dir . '/' . $filename);
             }
         }
+        closedir($dh);
         return true;
     }