diff --git a/lib/Caxy/HtmlDiff/AbstractDiff.php b/lib/Caxy/HtmlDiff/AbstractDiff.php
index ac4fff9..fe68cd3 100644
--- a/lib/Caxy/HtmlDiff/AbstractDiff.php
+++ b/lib/Caxy/HtmlDiff/AbstractDiff.php
@@ -140,7 +140,7 @@ public function initPurifier($defaultPurifierSerializerCache = null)
         // Cache.SerializerPermissions defaults to 0744.
         // This setting allows the cache files to be deleted by any user, as they are typically
         // created by the web/php user (www-user, php-fpm, etc.)
-        $HTMLPurifierConfig->set('Cache.SerializerPermissions', 0777);
+        $HTMLPurifierConfig->set('Cache.SerializerPermissions', 0775);
 
         $this->purifier = new HTMLPurifier($HTMLPurifierConfig);
     }