Verdi's last opera, Falstaff, was his first comic opera in over 50 years. Verdi and his librettist, Boito, kept the composition secret since Verdi was somewhat less comfortable with comic opera, and he wanted to have the option of canceling the production—even after the dress rehearsal. Boito's libretto has its basis in Shakespeare's The Merry Wives of Windsor with additional material from Henry VI, parts 1 and 2. The premiere at the Teatro alla Scala was a triumph, but, as always, Verdi continued to make adjustments to the score for both the Rome and Paris premieres; these changes were incorporated into the final version of the score.