By most accounts, “Harry Potter and the Cursed Child” is being well-received in London’s West End, as the continuation of the story fans know and love has opened to rave reviews from the likes of Variety and The Hollywood Reporter.

True die-hards, however, have picked up on what they’re calling a major inconsistency with the rest of the series. As a new debate rages on, there seems to be trouble brewing in Hogwarts. Read on for details, but beware: Spoilers ahead.

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In “Cursed Child,” the nature of the time-traveling device the “Time-Turner” has been altered, seemingly conflicting with its usage in “Harry Potter and the Prisoner of Azkaban.” On Reddit, hardcore fans have seized on this as not only a source of confusion and disappointment, but also the time-travel plot of “Cursed Child” as something of a betrayal.

In the “Azkaban” book and film, Hermione Granger used a Time-Turner to help double her class workload; later, she and Harry used one to prevent some deaths. In “Harry Potter and the Order of the Phoenix,” the Time-Turners are all destroyed, seemingly making it impossible for future generations of magicians to use them for time travel.

However, the plot of “Cursed Child” takes place 19 years after the last Potter adventure, following the sons of Harry and Draco Malfoy as they use a Time-Turner to mess with the past, “Back to the Future”-style. In doing so, they set off a butterfly effect — which contradicts author JK Rowling’s  previously-stated Time-Turner notion that the device works as a closed causal loop that can’t affect future events. Fans argue that if Time-Turners had existed the way “Cursed Child” describes them, Hermione and Harry’s previous actions would have had far-reaching consequences.

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“Like many others I’m really disappointed. I feel like Cursed Child was JKR’s answer to any ‘Well, why didn’t they just go back in time and fix __’ question,” writes @acciohagrid on Reddit. “But she already answered that in [‘Azkaban’] and had all the time turners smashed in [‘Order of the Phoenix’] to prevent any more meddling. The way she set up time travel in her universe, the stuff in Cursed Child is just not possible.”

Another user complains that this revisionist take on the plot device now renders many pieces of passionately-created fan fiction irrelevant. “When I first read about the time turner travel, my reaction was quite negative, too,” writes @InquisitorCOC, pointing to 115 fanfics that use the theme.

According to another fan, “Cursed Child” feels so out of sync with the rest of Rowling’s tales that it seems like it is fan fiction itself. “So many liberties have been taken with the time-turner,” writes @CosmetopiaDigest. “And so many contradictions have been made from what was stated in [‘Prisoner of Azkaban’], that this feels like one of those anything-is-possible fan-fics.”

So, does JK Rowling know that she has seemingly created a gaping plot hole in her universe? Does she care? “Harry Potter and the Cursed Child” is scheduled to hit bookstores July 31 in the form of a rehearsal script, so it seems unlikely that she’d even be able to fix those contradictions before they’re read by millions of fans. That is, unless she can get her hands on a Time-Turner.