A hedge fund is suing Royal Bank of Scotland over a promise allegedly made by ABN Amro.

London-based Merebis Capital Management has filed suit in London High Court, accusing ABN—which was acquired by RBS last year—of failing to pay a £17.8 million (US$35.6 million) penalty for early withdrawal, which Merebis claims it is owed under the terms of ABN’s investment.

According to Merebis, founded by four former ABN traders, RBS asked to redeem all of the €250 million (US$397.2 million) investment made in the fund by ABN, which seeded the new hedge fund last July. Merebis claims that ABN agreed to a three-year lockup at the time, subject to exceptions, and that it is entitled to a 10% early withdrawal penalty.

The hedge fund says it repaid most of the investment this month—the sell-off of portfolio holdings pushed the fund’s loss from 1.7% to 5.9%—but that its request for the £17.8 million penalty has not been met.

Merebis was forced to shutter the fund after filling RBS’ redemption request; it raised very little money aside from the €250 million in seed capital.