This paper studies a common-value first-price auction in which bidders are uncertain about the number of competitors they have. This uncertainty affects the nature of the inference from winning (”winner’s curse”). In particular, the expected value con- ditional on winning is usually not monotone and features a stronger winner’s curse at intermediate bids. Consequently, bidders have incentives to pool on common bids. At these pooling bids (”atoms”), payoffs change discontinuously. Due to this discontinuity, no equilibrium exists unless the expected number of bidders is sufficiently small. To the ensure the existence for any number of bidders, we extend the auction mechanism by a compound cheap talk message that enables bidders to indicate their eagerness to win. This extended auction mechanism can be used to easily derive properties for auctions on a discretized bidding space, where an equilibrium always exists.