Is the market salary based off other startups who have closed large rounds, or a FAANG company? It is common to be paid a bit less at a startup compared to a very large company. However if you feel you are being shortchanged it will likely result in friction with the company sooner or later.
Ask for more, worst case they come back with no, then you have to decide if you want to stay at that rate. Odds are your stock isn't going to be worth a lot, but I am a pessimist when it comes to equity.