Jon was lying down in his bed, staring at the ceiling, thinking once again about what happened with Karyn. It wasn't that he didn't trust Karyn; he wouldn't have shown her the stone otherwise, but her careless wishing made him realize how easily one could make wish he never meant. He was always alone when he had tested the stone, and so only talked to make wishes, but a slip of the tongue was too easy when talking to someone else.
It was bound to happen again sooner or later.
While he didn't dislike the result of Karyn's wish, the next time could have much bigger consequences. He had to do something about it!
He took the stone out of its box. "I wish this stone would only grant a wish if I confirm verbally that it's a wish."
The stone flashed briefly, confirming the wish had been granted, but he had to test it to be sure.
"I wish my computer would turn on." Nothing happened for a few seconds. "This is a wish." He added, and his computer came to life. Jon smiled, not only would it prevent future mistakes from happening, but he could stop Karyn or anyone else from making wishes he didn't like.
It was a great wish!