diff --git a/src/opnsense/mvc/app/library/OPNsense/Core/Config.php b/src/opnsense/mvc/app/library/OPNsense/Core/Config.php
index fd55ccd4b..ec9177bcd 100644
--- a/src/opnsense/mvc/app/library/OPNsense/Core/Config.php
+++ b/src/opnsense/mvc/app/library/OPNsense/Core/Config.php
@@ -626,7 +626,7 @@ class Config extends Singleton
      */
     private function overwrite($filename)
     {
-        $fhandle = fopen($this->config_file, "r+");
+        $fhandle = fopen($this->config_file, "a+e");
         if (flock($fhandle, LOCK_EX)) {
             fseek($fhandle, 0);
             chmod($this->config_file, 0640);