In the public market, bad news for a company typically sends its stock plunging. In the private market, of course, there’s no opportunity for such an immediate reaction. But the growing number of institutional investors in private companies can still take their own writedowns, providing a window into how valuations in the private tech sector can fall as well as rise.

Data analytics company MongoDB, for instance, announced earlier this year it raised $80 million, increasing the reported valuation of the private company to $1.6 billion from $1.2 billion. But public filings by its investors tell a less rosy story.