diff --git a/apps/emqx_lwm2m/src/emqx_lwm2m_protocol.erl b/apps/emqx_lwm2m/src/emqx_lwm2m_protocol.erl
index 0a40d3765..39eef75ae 100644
--- a/apps/emqx_lwm2m/src/emqx_lwm2m_protocol.erl
+++ b/apps/emqx_lwm2m/src/emqx_lwm2m_protocol.erl
@@ -407,8 +407,8 @@ clientinfo(#lwm2m_state{peername = {PeerHost, _},
       peerhost => PeerHost,
       sockport => 5683,         %% FIXME:
       clientid => EndpointName,
-      username => null,
-      password => null,
+      username => undefined,
+      password => undefined,
       peercert => nossl,
       is_bridge => false,
       is_superuser => false,