diff --git a/source/_docs/asterisk_mbox.markdown b/source/_docs/asterisk_mbox.markdown
index 8c6ba581112..a36c5439dcb 100644
--- a/source/_docs/asterisk_mbox.markdown
+++ b/source/_docs/asterisk_mbox.markdown
@@ -92,7 +92,7 @@ Before beginning make sure that you have the following:
    Type=simple
    User=asterisk
    Group=asterisk
-   ExecStart=/usr/local/bin/asterisk_mbox_server -cfg /etc/asterisk/asterisk_mbox.ini
+   ExecStart=/usr/local/bin/asterisk_mbox_server --cfg /etc/asterisk/asterisk_mbox.ini
    Restart=on-failure
 
    [Install]