case erlang:function_exported(rebar3, main, 1) of
    true -> % rebar3
        CONFIG;
    false -> % rebar 2.x
        [{deps, [
            {gun, ".*", {git, "https://github.com/ninenines/gun.git", "2.0.0"}}
        ]} | lists:keydelete(deps, 1, CONFIG)]
end.