Using singlequotes with _()

Hi, I've been doing some scripts which I will now start to translate using gettext. I have used _() on a lot of places to mark the string which needs translation. The problem seems to be that I have used _('Translate this') instead of _("Translate this") . xgettext doesnt seem to understand that this is the same thing in php, I could probably run around and change all ' to ", but I'd like to keep them if its possible. Is it possible to get xgettext to understand this, or is there some other tool to create .po files? Best regards, Eric