Is it normal for a startup law firm to ask for a nominal amount of stock in exchange for deferring fees?

I recently asked the law firm performing our incorporation if they would be willing to defer fees until funding.

The lead attorney at the firm stated that they will consider deferring fees until we raise capital in exchange for a nominal amount of stock in our startup, and that the deferral would not apply to the incorporation package and filing fees.

This surprised me a little as I thought that most firms simply defer the fee until funding but factor in a higher price for their services to offset the risk. Is it still normal for a law firm to ask for stock in exchange for fee deferral?