Why does Nawawi's Forty Hadith contain 42 ahadith?

"[An-Nawawi's Forty Hadith](http://en.wikipedia.org/wiki/Al-nawawi%27s_forty_hadiths) " has always been my favorite book of ahadith; it was the first one I ever bought and remains highly recommended reading for anyone interested in the fundamentals of Islam. However, one thing about this compilation has always bothered me; despite being entitled "Forty Hadith", my copy obviously contains 42 ahadith. I had originally thought this may just be a quirk of translation (my copy is translated by Ezzeddin Ibrahim and Denys Johnson-Davies), but I have seen the same 42-hadith breakdown used in [Sunnah.com's collection](http://www.sunnah.com/nawawi40) ; not sure which translator they used, but the translation is clearly different from my own copy. Having never read the original Arabic compilation, I can't be certain that this isn't yet a translation quirk, but two separate translations with the same clearly-defined numbering scheme casts doubt on that theory. Presumably, in addition to being one of the most celebrated scholars in Shafi'i jurisprudence, [Imam An-nawawi](http://en.wikipedia.org/wiki/Imam_al-Nawawi) was at least basically competent in counting. Which leaves me scratching my head over the question, **why does his famous Forty Hadith have two too many *ahadith*?** This might seem a silly question, but it's really been driving me nuts for a while.