The binding on [`node_buffer.ml`](https://github.com/BuckleScript/bucklescript/blob/master/jscomp/others/node_buffer.ml) is ``` external toString : t -> string = "" [@@bs.send] [@@bs.scope "Buffer"] ``` The `[@@bs.scope "Buffer"]` is causing the js output to have undefined value. For example, ``` Node.Buffer.toString(something); // js output, Buffer is undefined something.Buffer.toString(); ```