Investors looking to boost their returns have long attached strings to how private tech companies can sell or go public. But those purse strings can look more like chains as more high-value companies offer investors concessions like the right to block IPOs or accrue dividends paid out in an acquisition.

Twenty-four percent of high-value companies raising money in the fourth and first quarters granted investors the right to veto an IPO if it’s not priced at a high enough valuation. That’s up from 15% in the three quarters before that.