diff --git a/doc/user/zebra.rst b/doc/user/zebra.rst
index 9ed6b6dd7f..f65455b959 100644
--- a/doc/user/zebra.rst
+++ b/doc/user/zebra.rst
@@ -78,6 +78,11 @@ Besides the common invocation options (:ref:`common-invocation-options`), the
    protocols about route installation/update on ack received from
    the linux kernel or from offload notification.
 
+.. option:: -s <SIZE>, --nl-bufsize <SIZE>
+
+   Allow zebra to modify the default receive buffer size to SIZE
+   in bytes.  Under *BSD only the -s option is available.
+
 .. _interface-commands:
 
 Configuration Addresses behaviour