This is correct. Since you were informed that late, compensation is due if your arrival time was more than 2 hours later than the original one, unless AF can "can prove that the cancellation [was] caused by extraordinary circumstances which could not have been avoided even if all reasonable measures had been taken."
In the first place, you should get in touch with AF customer relations and ask them for compensation for the cancellation of your flight in accordance with the provisions of EU Regulation 261/2004.
If you want more info on the rules, do a search in this forum (or that of any other European airline, for that matter).