Stash, a digital investment platform geared toward millennials, has launched a novel rewards program that delivers fractional shares of a stock or of a global stock ETF instead of points.

When a client uses their Stash debit card for purchases, a minimum 0.125% of the money spent is invested in the stock of the company selling the goods or service, if it’s publicly traded. Otherwise the 0.125% is invested in the Vanguard Total World Stock ETF (VT), which is available on the Stash platform. Accounts will be credited with fractional shares within two to five business days.

The program, known as Stock-Back, marks the official launch of Stash’s mobile-first banking services in partnership with Green Dot Bank and its parent company, Green Dot Corp.

Stash says it will quickly ramp up rewards, which can run up to 5% when layered with exclusive offers and partner deals, according to Stash. No minimum purchase amount is required but purchases of gift cards, prepaid cards and money orders will not qualify for rewards.

“We’re trying to upend an ecosystem where financial services companies continue to take from the masses, and pile on fee after fee,” CEO and Co-Founder Brandon Krieg said in a statement. “At Stash, we believe the customer should keep more of their money, which is why we built a unique rewards program that invests in them when they spend.”

Stock-Back is the latest innovation of Stash, which launched in October 2015. It follows a funding round of $65 million — it has raised a total $181.3 million, according to Crunchbase — and the rollout of a suite of new features including roundups. When a client makes a purchase for $9.55 with a Stash debit card, which rounds up to $10, the additional 45 cents is eventually deposited in a clients’ cash balance accounts when roundups total $5.

“There are two fintech companies that are being the most successful encouraging individuals to save and invest, Stash and Acorns,” says David Goldstone, research analyst at Backend Benchmarking, which produces The Robo Report.

“Stash’s success at attracting users and introducing them to investing for the first time is a result of their innovative approach to engaging customers with recommendations based on their personal interests and spending habits.”

Goldstone adds that the company’s new rewards program “will add additional incentives and encouragement for users to save and invest. [But its] base reward rate of 0.125% is “quite low”… [and] suggesting investments based on user’s interests or spending habits  … is probably not the best method for building an efficient, high performing portfolio.”