diff --git a/apps/emqx_authz/src/emqx_authz_api_sources.erl b/apps/emqx_authz/src/emqx_authz_api_sources.erl
index d93c469f5..e0d4667cb 100644
--- a/apps/emqx_authz/src/emqx_authz_api_sources.erl
+++ b/apps/emqx_authz/src/emqx_authz_api_sources.erl
@@ -428,22 +428,22 @@ update_config(Cmd, Sources) ->
     end.
 
 read_cert(#{<<"ssl">> := #{<<"enable">> := true} = SSL} = Source) ->
-    CaCert = case file:read_file(maps:get(cacertfile, SSL, "")) of
+    CaCert = case file:read_file(maps:get(<<"cacertfile">>, SSL, "")) of
                  {ok, CaCert0} -> CaCert0;
                  _ -> ""
              end,
-    Cert =   case file:read_file(maps:get(certfile, SSL, "")) of
+    Cert =   case file:read_file(maps:get(<<"certfile">>, SSL, "")) of
                  {ok, Cert0} -> Cert0;
                  _ -> ""
              end,
-    Key =   case file:read_file(maps:get(keyfile, SSL, "")) of
+    Key =   case file:read_file(maps:get(<<"keyfile">>, SSL, "")) of
                  {ok, Key0} -> Key0;
                  _ -> ""
              end,
-    Source#{ssl => SSL#{cacertfile => CaCert,
-                        certfile => Cert,
-                        keyfile => Key
-                       }
+    Source#{<<"ssl">> => SSL#{<<"cacertfile">> => CaCert,
+                              <<"certfile">> => Cert,
+                              <<"keyfile">> => Key
+                             }
            };
 read_cert(Source) -> Source.