British digital lender Revolut has broken even for the first time, in a rare development for a niche sector that has struggled with profitability.

Revolut said Monday that it had broken even for the first time in December, and that its monthly transaction volume surged to $1.5 billion, an increase of over 700 percent in the last 12 months.

The start-up has signed up a total of 1.5 million users to its mobile app, up 50 percent from a figure it achieved in November.

The firm declined to disclose any figures on revenues or losses, and said it made no sense to do so due to the competitive market it operates in.

Revolut’s app lets customers open a current account in 60 seconds, and offers currency exchange at the interbank rate. Last year, the start-up introduced a feature that let users buy, hold and sell cryptocurrencies including bitcoin, ethereum and litecoin.

It claims it is the first digital challenger bank to break even. Challenger banks are small banking groups, predominantly based in the U.K., set up with the aim of competing with larger lenders.

Britain’s Monzo and Germany’s N26 are among such start-up lenders that have faced difficulty in turning user growth into profit.

However, new European rules that open up the data of big banks to third party firms could point to increased competitiveness for fintech start-ups and big tech firms.

Revolut applied for a European banking license in November, and looks to provide deposit and credit services under that regulatory framework.

The firm said it plans to expand to the U.S. and Canada within the next few months. It will subsequently launch in Singapore, Hong Kong, Australia, New Zealand, India and Brazil.

“Whilst it is encouraging to see that our business model is working, becoming a profitable business is not our priority right now,” Revolut co-founder and CEO Nikolay Storonsky said in a statement Monday.

“We are completely focused on expanding Revolut to as many countries around the world as possible, with the United States, Singapore and Australia almost ready to go.”