Are japanese psn ps1 games region locked for the psp?

I've heard recentley that you cannot play downloaded ps1 games from the japanese ps store on US psps bcuz of a recent firmware update. I cant find any info on from google though, so are they locked or not? cuz there are some ps1 games i really wanted to get off the japanese ps store... If they are thats a stupid movie on sonys part, one of the coolest things about the psp was that it was region free. Yet another reason im re-considering buying the go.