Workplace messaging app Slack has raised $250 million in a funding round led by the Japanese tech giant SoftBank, putting its overall valuation at $5.1 billion.

SoftBank said Monday that its Vision Fund led a Series G funding round alongside Accel and other investors, topping up its existing $540 million in funding to $790 million.

“Slack is the operating system for today’s fast moving businesses, enabling teams to work together effectively at a time when businesses need to be responsive to rapid change and disruption,” Deep Nishar, senior managing partner at the SoftBank Vision Fund, said in a statement Monday.

“The Vision Fund is excited to invest in Slack and support its mission to help millions of people, teams and companies collaborate and communicate.”

Capital raised by the investment will serve as an effective “war chest” of funds, SoftBank Vision Fund said in an emailed statement, enabling Slack to look to expanding further internationally.

SoftBank Vision Fund added that it would also help to navigate the start-up through “potential future macro-economic uncertainty”.

Slack’s chief executive said the latest funding would help transform the firm’s business model to start generating cash.

“We believe that Slack is the future of work, and this fund reinforces that – providing long-term operational flexibility and resources that prepare us to run Slack as a cash-generating company and move quickly as the market evolves,” Slack CEO and Founder Stewart Butterfield said in a statement Monday.

Slack is one of the latest tech start-ups to receive millions in cash from SoftBank.

The Japanese conglomerate has invested aggressively in a number of firms, including another workplace-focused firm, WeWork.

SoftBank launched its Vision Fund in May. The group of investors incudes Saudi Arabia’s public investment fund, Apple and Qualcomm.

It has also been reported that Uber could be nearing a deal to receive billions of dollars in funding from the fund.