Should I ask for more money?

Just received a verbal offer for a job I'm pretty excited about. Only issue is they offered me 5% below what I'm currently making. There was no discussion of current salary or salary requirements so their offer was just a number they came up with. They said that I would also receive a discretionary bonus but didn't comment on a potential percentage range. Obviously I'm not going to make any moves until I have an offer letter in hand but I was wondering if I should go back and ask them to match my current salary? I'm going to try to get more information regarding the potential bonus size because that will play a big factor but at the same time it's not guaranteed. I should also note that I feel like I'm underpaid in my current role so I was hoping to get at least a 5% bump. Just wondering how I should proceed. Thanks in advance.