I think that spec is wrong, but I do see one place at [L135](https://github.com/basho/riak_kv/blob/feature/riak-object-btype-hash-metadata/src/riak_object.erl#L135) where you could get something other than a `dict` stored for that field. If someone used `new/4` to specify metadata and the function clauses at [L118](https://github.com/basho/riak_kv/blob/feature/riak-object-btype-hash-metadata/src/riak_object.erl#L118) or [L120](https://github.com/basho/riak_kv/blob/feature/riak-object-btype-hash-metadata/src/riak_object.erl#L120) when creating the object they could pass any sort of non-list structure in for `MD`. The `is_list` guards in previous function clauses would not let a list make it that far though so that gives more credence to the idea that the spec is wrong.