unexpected overlap in comment with round_trip_load()

[skhomuti]

ruyaml.round_trip_load causes following error, but yaml hasn't contain any comments

NotImplementedError: overlap in comment [None, [CommentToken('\n', line: 2, col: 0)]] [None, [CommentToken('\n', line: 4, col: 0)]]

- config:
      key: {default: 123}

-

    config: 123

load() and safe_load() works fine