Here's Maggie, aged 7. She's not happy.
Maggie's mum, Karen, says she saw the sign at the Tower Park branch in Poole, Dorset.
She tells BuzzFeed News she's a big fan of Batman, Superman, Spider Man, Wonder Woman and she loves The Flash TV series. She says:
She spotted the sign before I did and pointed it out to me by indignantly saying something like, "Well that's wrong! Anybody can like superheroes, they're being stupid aren't they?"
Tesco told BuzzFeed News: "This alarm clock would make a great gift for both girls and boys. The sign has been removed and we're sorry if it caused any confusion."
She says that the more Maggie reads, the more she's begun to notice this sort of thing:
Fortunately it doesn't seem to have put her off - as well as superheroes she loves Doctor Who, Minecraft, dragons, skeletons and zombies (she had a cemetery cake for her birthday!) but also likes Frozen, princesses, kittens etc. She just thinks shops labelliing toys for boys or girls is silly: "I can like what I want."
Maggie's mum tells BuzzFeed News that Tesco has confirmed the sign will be removed. She says: "I asked if it would be in all stores but they haven't yet replied." BuzzFeed News is still attempting to ascertain if this will be the case.
Tesco has confirmed to BuzzFeed News the sign will be removed from all stores.