diff --git a/helper.php b/helper.php
index e64681b..ffd3d99 100644
--- a/helper.php
+++ b/helper.php
@@ -12,7 +12,7 @@
  * It implements the dependency handling mechanism that is needed for the
  * rrd INCLUDE tag.
  */
-class cache_rrdgraphbase extends cache {
+abstract class cache_rrdgraphbase extends cache {
 	/** @var String Page-Number of the page that is managed by this cache instance. */
     private $pageId;
     
@@ -26,7 +26,7 @@ class cache_rrdgraphbase extends cache {
      * @param String $key Uniq value identifying the cached content on the page provied by $pageId. The identifier is hashed before being used.
      * @param String $ext The extension of the cache file.
      */
-    protected function __construct($pluginName, $pageId, $key, $ext) {
+    public function __construct($pluginName, $pageId, $key, $ext) {
         $this->pageId = $pageId;
         $this->pluginName = $pluginName;
         
diff --git a/plugin.info.txt b/plugin.info.txt
index b0204db..578da4e 100644
--- a/plugin.info.txt
+++ b/plugin.info.txt
@@ -1,7 +1,7 @@
 base   rrdgraph
 author Daniel Goß
 email  developer@flashsystems.de
-date   2015-04-04
+date   2015-10-10
 name   RRD graph generator
 desc   This plugin creates graphs from RRD tool data. Uses php5-rrd to generate the images.
 url    https://github.com/FlashSystems/rrdgraph