On Saturday Potter fansites were very excited as it looked like someone had accessed a secret bit of JK Rowling's website that gave away the title.
It claimed the next book was called Harry Potter and the Pillar of Storgé and looked like it might be real.
But now fans have had time to look into it more closely, many of them are convinced it was a very clever hoax.
They said that behind that door was a message from JK Rowling herself dated 1 July that revealed the title.
There was even a video clip that looked just like the other bits of the site, which at first convinced some people.
But some of the things in that video clip didn't look right to Potter fans.
They say it uses some American-style spelling and punctuation, which JK hasn't used when writing on her site before.
And although the video looks right at first, some of the things in it aren't the same as other bits on JK's site.
Newsround's website is still trying to get official information on whether it's real or not, and as soon as we do, we'll let you know too.
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