diff --git a/app/code/core/Mage/Adminhtml/Block/Dashboard/Graph.php b/app/code/core/Mage/Adminhtml/Block/Dashboard/Graph.php
index b6d72c0f1eb..da1b14a8799 100644
--- a/app/code/core/Mage/Adminhtml/Block/Dashboard/Graph.php
+++ b/app/code/core/Mage/Adminhtml/Block/Dashboard/Graph.php
@@ -444,7 +444,7 @@ public function getChartUrl($directUrl = true)
             }
             return self::API_URL . '?' . implode('&', $p);
         } else {
-            $gaData = urlencode(base64_encode(serialize($params)));
+            $gaData = urlencode(base64_encode(json_encode($params)));
             $gaHash = Mage::helper('adminhtml/dashboard_data')->getChartDataHash($gaData);
             $params = array('ga' => $gaData, 'h' => $gaHash);
             return $this->getUrl('*/*/tunnel', array('_query' => $params));
diff --git a/app/code/core/Mage/Adminhtml/controllers/DashboardController.php b/app/code/core/Mage/Adminhtml/controllers/DashboardController.php
index 09ffc4c6f8b..ab2d65472a2 100644
--- a/app/code/core/Mage/Adminhtml/controllers/DashboardController.php
+++ b/app/code/core/Mage/Adminhtml/controllers/DashboardController.php
@@ -92,7 +92,8 @@ public function tunnelAction()
         if ($gaData && $gaHash) {
             $newHash = Mage::helper('adminhtml/dashboard_data')->getChartDataHash($gaData);
             if ($newHash == $gaHash) {
-                if ($params = unserialize(base64_decode(urldecode($gaData)))) {
+                $params = json_decode(base64_decode(urldecode($gaData)), true);
+                if ($params) {
                     $response = $httpClient->setUri(Mage_Adminhtml_Block_Dashboard_Graph::API_URL)
                             ->setParameterGet($params)
                             ->setConfig(array('timeout' => 5))