A U.S. Appeals Court today unanimously overturned a lower court’s 2009 decision to dismiss an investor lawsuit against Blackstone (BX), ruling that the plaintiff’s “plausibly allege” that Blackstone omitted “material information” related to its investments in FGIC and Freescale Semiconductor.

FGIC is a bond insurer acquired by Blackstone in 2003, which was subsequently damaged by the subprime mortgage market crash. Freescale is a chip-maker that Blackstone wrote off several years after its 2006 investment, but which since has rebounded to the point that it recently hired banks to manage its IPO.

Plaintiffs had argued that Blackstone was required to disclose details of both investments, while Blackstone countered that it was not required to provide information about all of non-material investments that underly its various funds (of which it regularly discloses top-line performance data).

The original judge sided with Blackstone, but today’s ruling included the following line: “We see no principled basis for holding that an historically ‘private’ equity company that has chosen to go public is somehow subject to a different standard under the securities disclosure laws and regulations than a traditional public company with numerous subsidiaries.”

Blackstone, of course, plans to keep fighting. A spokesman tells Fortune that “the plaintiffs’ allegations are totally without merit and we will defend this suit vigorously.”

View today’s entire ruling below:

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