There are many things you wouldn't want to see when walking into your hotel room - another guest in bed, for example, or any kind of dirty laundry or rubbish strewn anywhere.
But one hotel guest claims to have found a secret note which probably REALLY put them off their sleep.
An image of the letter, written on a hotel's notepad paper, was posted to Reddit along with the caption: "Heard something crinkle when I settled in for the night..."
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The note was supposedly written by the previous guest, and says: "If you're reading this then housekeeping did not change your sheets!"
Yuck.
Of course, there's no evidence that the poster didn't write this themselves as a funny joke to post online, and it's not clear where in the world this was taken - but the pad paper does have the Courtyard Marriott logo on.
Mirror Online contacted Marriott for comment. A spokesperson said: "While there is no way for us to verify validity of this claim, Marriott has the greatest concern and respect for every guest’s experience.
"We take hotel hygiene and cleanliness very seriously. As a result, Marriott has established very strict standards of cleanliness for all its hotels.
"In the unusual event a guest makes us aware of a concern, we respond immediately to the situation and take the appropriate steps to remedy the problem."