If I buy 100 shares of a capital asset, and 3 days later sell 50 shares for a loss, is the loss disallowed because of the wash sale rule?

I'm thinking it might, because if you imagine taking the 100 shares and splitting it into two lots of 50, Lot A, and Lot B, when you sell Lot A three days later, then Lot B would be 50 shares bought within the +/- 30 day time frame.