Missing ExtraData in Quote

[iolivergithub]

The current definition of Quote is (line 991)
func Quote(rw io.ReadWriter, signingHandle tpmutil.Handle, signerAuth, unused string, toQuote []byte, sel PCRSelection, sigAlg Algorithm) ([]byte, *Signature, error) {
// TODO: Remove "unused" parameter on next breaking change.

I'm assuming that toQuote []byte is used for any extra data?

However the resulting field ExtraData in AttestationQuoteInfo contains a nil (or null when rendered into JSON).