diff --git a/apps/emqx_dashboard/src/emqx_dashboard_swagger.erl b/apps/emqx_dashboard/src/emqx_dashboard_swagger.erl
index f128513ba..018101338 100644
--- a/apps/emqx_dashboard/src/emqx_dashboard_swagger.erl
+++ b/apps/emqx_dashboard/src/emqx_dashboard_swagger.erl
@@ -959,7 +959,7 @@ to_bin(List) when is_list(List) ->
 to_bin(Boolean) when is_boolean(Boolean) -> Boolean;
 to_bin(Atom) when is_atom(Atom) -> atom_to_binary(Atom, utf8);
 to_bin({Type, Args}) ->
-    unicode:characters_to_binary(io_lib:format("~ts(~p)", [Type, Args]));
+    unicode:characters_to_binary(io_lib:format("~ts-~p", [Type, Args]));
 to_bin(X) ->
     X.