diff --git a/module/common/model.php b/module/common/model.php
index acd30bd074..71db8fdb54 100644
--- a/module/common/model.php
+++ b/module/common/model.php
@@ -1405,6 +1405,20 @@ EOD;
         return $hasField;
     }
 
+    /**
+     * Check safe file.
+     *
+     * @access public
+     * @return string|false
+     */
+    public function checkSafeFile()
+    {
+        if($this->app->getModuleName() == 'upgrade' and $this->session->upgrading) return false;
+
+        $statusFile = $this->app->getAppRoot() . 'www' . DIRECTORY_SEPARATOR . 'ok.txt';
+        return (!is_file($statusFile) or (time() - filemtime($statusFile)) > 3600) ? $statusFile : false;
+    }
+
     /**
      * Check upgrade's status file is ok or not.
      *
@@ -1413,7 +1427,7 @@ EOD;
      */
     public function checkUpgradeStatus()
     {
-        $statusFile = $this->loadModel('upgrade')->checkSafeFile();
+        $statusFile = $this->checkSafeFile();
         if($statusFile)
         {
             $cmd = strtoupper(substr(PHP_OS, 0, 3)) === 'WIN' ? $this->lang->upgrade->createFileWinCMD : $this->lang->upgrade->createFileLinuxCMD;
diff --git a/module/extension/control.php b/module/extension/control.php
index 4b4235981d..74de34681c 100644
--- a/module/extension/control.php
+++ b/module/extension/control.php
@@ -121,7 +121,7 @@ class extension extends control
         $this->view->title       = $installTitle . $extension;
 
         
-        $statusFile = $this->loadModel('upgrade')->checkSafeFile();
+        $statusFile = $this->loadModel('common')->checkSafeFile();
         if($statusFile)
         {
             $this->view->error = sprintf($this->lang->extension->noticeOkFile, $statusFile);
@@ -427,7 +427,7 @@ class extension extends control
      */
     public function upload()
     {
-        $statusFile = $this->loadModel('upgrade')->checkSafeFile();
+        $statusFile = $this->loadModel('common')->checkSafeFile();
         if($statusFile)
         {
             $this->view->error = sprintf($this->lang->extension->noticeOkFile, $statusFile);
diff --git a/module/upgrade/model.php b/module/upgrade/model.php
index af6740c48d..0743d048d3 100644
--- a/module/upgrade/model.php
+++ b/module/upgrade/model.php
@@ -2662,9 +2662,7 @@ class upgradeModel extends model
      */
     public function checkSafeFile()
     {
-        if($this->app->getModuleName() == 'upgrade' and $this->session->upgrading) return false;
-        $statusFile = $this->app->getAppRoot() . 'www' . DIRECTORY_SEPARATOR . 'ok.txt';
-        return (!is_file($statusFile) or (time() - filemtime($statusFile)) > 3600) ? $statusFile : false;
+        return $this->loadModel('common')->checkSafeFile();
     }
 
     /**