Popular workplace collaboration app Slack has raised a new round of financing, led by SoftBank, which has subsequently valued the Silicon Valley start-up at $5.1bn.
The financing round received $250mn in funding and most of that came from SoftBank's Vision Fund, as the telecommunications giant invests billions in technology start-ups.
Led by Japan's richest man, Masayoshi Son, SoftBank's $93bn Vision Fund helped lift Slack's fundraising total to $841mn.
This makes Slack one of the leading business software start-ups, whilst it reported an annual recurring revenue of $200mn last week.
Stewart Butterfield, chief executive of Slack, did note that it's a "strange world" as they have not gone public yet.
Instead, an IPO seems destined for 2018 after Butterfield said he was reluctant to bring the company public, as there is a risk the company could fail to meet targets due to its relative infancy.