The Series G funding, reported by Bloomberg, puts the popular chat application at a $5 billion valuation, a big step up from the $3.8 billion valuation Slack had at its last funding round in April 2016.
It's a big milestone for Slack, which currently has about $1 billion in revenues, although the amount of money raised is half of what early reports had anticipated.
The company was previously expected to rake in $500 million at a $5 billion valuation. It's also been rumored that Amazon, Microsoft, and Google were all interested in acquiring the startup.
If an acquisition had gone through, it would be have represented a major strategic shift for the company, which Slack CEO Stewart Butterfield has repeatedly signaled he plans to keep independent.
Slack declined to comment.
This post originally appeared on Business Insider.