diff --git a/system/src/Grav/Common/Session.php b/system/src/Grav/Common/Session.php
index 2b3469178..5be15ec35 100644
--- a/system/src/Grav/Common/Session.php
+++ b/system/src/Grav/Common/Session.php
@@ -45,7 +45,7 @@ class Session extends \RocketTheme\Toolbox\Session\Session
             );
 
             $unique_identifier = GRAV_ROOT;
-            $this->setName($config->get('system.session.name', 'grav_site') . '_' . substr(md5($unique_identifier), 0, 7) . ($is_admin ? '_admin' : ''));
+            $this->setName($config->get('system.session.name', 'grav_site') . '-' . substr(md5($unique_identifier), 0, 7) . ($is_admin ? '-admin' : ''));
             $this->start();
             setcookie(session_name(), session_id(), time() + $session_timeout, $session_path);
         }