diff --git a/library/Zend/Cache/Core.php b/library/Zend/Cache/Core.php
index 55af061257..685d5d52b6 100644
--- a/library/Zend/Cache/Core.php
+++ b/library/Zend/Cache/Core.php
@@ -300,7 +300,7 @@ public function load($id, $doNotTestCacheValidity = false, $doNotUnserialize = f
         }
         $id = $this->_id($id); // cache id may need prefix
         $this->_lastId = $id;
-        self::_validateIdOrTag($id);
+        $this->_validateIdOrTag($id);
 
         $this->_log("Zend_Cache_Core: load item '{$id}'", 7);
         $data = $this->_backend->load($id, $doNotTestCacheValidity);
@@ -327,7 +327,7 @@ public function test($id)
             return false;
         }
         $id = $this->_id($id); // cache id may need prefix
-        self::_validateIdOrTag($id);
+        $this->_validateIdOrTag($id);
         $this->_lastId = $id;
 
         $this->_log("Zend_Cache_Core: test item '{$id}'", 7);
@@ -355,8 +355,8 @@ public function save($data, $id = null, $tags = array(), $specificLifetime = fal
         } else {
             $id = $this->_id($id);
         }
-        self::_validateIdOrTag($id);
-        self::_validateTagsArray($tags);
+        $this->_validateIdOrTag($id);
+        $this->_validateTagsArray($tags);
         if ($this->_options['automatic_serialization']) {
             // we need to serialize datas before storing them
             $data = serialize($data);
@@ -424,7 +424,7 @@ public function remove($id)
             return true;
         }
         $id = $this->_id($id); // cache id may need prefix
-        self::_validateIdOrTag($id);
+        $this->_validateIdOrTag($id);
 
         $this->_log("Zend_Cache_Core: remove item '{$id}'", 7);
         return $this->_backend->remove($id);
@@ -460,7 +460,7 @@ public function clean($mode = 'all', $tags = array())
                                    Zend_Cache::CLEANING_MODE_MATCHING_ANY_TAG))) {
             Zend_Cache::throwException('Invalid cleaning mode');
         }
-        self::_validateTagsArray($tags);
+        $this->_validateTagsArray($tags);
 
         return $this->_backend->clean($mode, $tags);
     }
@@ -667,7 +667,7 @@ public function touch($id, $extraLifetime)
      * @throws Zend_Cache_Exception
      * @return void
      */
-    protected static function _validateIdOrTag($string)
+    protected function _validateIdOrTag($string)
     {
         if (!is_string($string)) {
             Zend_Cache::throwException('Invalid id or tag : must be a string');
@@ -689,13 +689,13 @@ protected static function _validateIdOrTag($string)
      * @throws Zend_Cache_Exception
      * @return void
      */
-    protected static function _validateTagsArray($tags)
+    protected function _validateTagsArray($tags)
     {
         if (!is_array($tags)) {
             Zend_Cache::throwException('Invalid tags array : must be an array');
         }
         foreach($tags as $tag) {
-            self::_validateIdOrTag($tag);
+            $this->_validateIdOrTag($tag);
         }
         reset($tags);
     }