(NYTIMES) - Determined to avoid a repeat of the envelope snafu that resulted in a stunning Oscar best picture mix-up last year, new rules have been adopted by PwC, the accounting firm that tabulates votes for the Academy of Motion Picture Arts and Sciences.

The changes, which were first reported Monday by The Associated Press and have been confirmed by the academy and PwC, include having presenters ensure before going onstage that they have the correct envelope in hand; this will be confirmed beforehand by stage managers, too.

Last year, one of the two PwC representatives attending the Oscars mistakenly handed Warren Beatty, who was presenting the best picture award with Faye Dunaway, the backup envelope for best actress, which had moments earlier gone to Emma Stone for La La Land. After Beatty opened the envelope onstage, he hesitated, and Dunaway, thinking he was monkeying around, ended up reading out La La Land. In fact, Moonlight had won, but long moments passed before the bewildering mistake, and the correct winner, were revealed.

Last year's PwC accountants, Brian Cullinan and Martha Ruiz, have been replaced by Rick Rosas, a longtime PwC accountant who handled the Oscars envelopes for 14 years, and his colleague Kimberly Bourdon. (Both Cullinan and Ruiz still work at PwC.) A third PwC accountant, who also will have memorised the winners' list, will sit in the control room with the producers of the show. All three accountants will also attend rehearsals, and practice what to do if there's another mistake.

Perhaps the most drastic change of all: the PwC accountants won't be allowed to use their cellphones or be on social media during the ceremony. Last year, just before handing Beatty the wrong envelope, Cullinan tweeted out a photo of a jubilant Stone.

Oscar nominations will be announced Tuesday; the ceremony will be held March 4.