According to the Observer, the change was prompted by a newspaper column by novelist Philip Hensher, who wrote, after watching a rehearsal, "to see a revival of 'blacking up' in the opera house in 2005 is just beyond belief."
ROH spokesman Christopher Millard told the paper, "There are sensitivities we are aware of and it is best if she is not blacked up. We didn't feel comfortable with it, so it has gone."
Blackface, long ended in the United State, remains relatively common in European opera, where there are few black singers to play Otello and other explicitly black roles. Ulrica is described in the libretto for Un ballo as a "Negro fortuneteller."