Blackstone is joining investors in Diligent in a deal that values the maker of corporate-governance software at north of $4bn, according to a person familiar with the matter.

The largest portion of the roughly $500m investment was contributed by Clearlake Capital, which increased its previous stake in the company, the person said. The remainder came from Blackstone and some limited partners of Insight Partners, a New York firm that remains Diligent’s largest investor.