Private equity firm Apollo-owned Aspen Insurance on Wednesday filed its paperwork for an initial public offering in the United States, according to a regulatory filing.

The company did not disclose details about the size of the offering, but is reportedly targeting a $4 billion valuation. It also did not provide details about the exchange where it plans to list its shares.

Aspen went private in 2019, after funds affiliated to Apollo Global Management APO.N agreed to buy it in an all-cash deal valued at $2.6 billion.

The listing will test investor appetite for the sector, which was strong in the first half of the year but has tempered down in recent market debuts. 

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