Can you spot what's wrong with this Tinder selfie?

Stand-up comedian Dalia Malek was left shocked after she spotted something unexpected in this Tinder selfie. Photo / Tinder

Checking the background of your photo is the golden rule of all mirror selfies before sending them out to the world — however, this lad obviously didn't check before hitting publish.

A woman got a shock of a lifetime when she realised there was a naked man in her Tinder match's profile pic.

Stand-up comedian Dalia Malek from San Francisco shared the image on Twitter, joking that she found her "soulmate".

She even messaged the guy on Tinder, who was posing in the gym changing rooms, that the man in the background "has his whole d*** out", but he obviously didn't understand and said "f*** u" back.

Malek's 350,000 followers found the post hilarious with one commenting: "I would have said 'so can I get the background dude's number?'"

One woman got a shock of a lifetime when she realised there was a naked man in her Tinder match's profile pic. Photo / Twitter

Another replied: "You have a good eye for the small details."

Other users were confused as to he used that particular image in the first place.

"Why did he think this was a good picture to use?" one asked.

"Were all the others so bad that this one where a guy has his whole d*** out in the background was acceptable to him?" another chimed in.

One wondered why he was so "mad" that Dalia had pointed it out, while another said: "This is why most gyms say no phones/cameras in the locker rooms."

Other hilarious responses continued to pour in, with some believing that the profile actually belonged to the naked man in the background.

"Plot twist, what if the profile belongs to the guy in the background?" they wrote.

Some questioned the naked man's clothing method.

"Why be putting socks on before underwear?" one person wrote.

While another agreed: "Who puts socks on before underwear? Or are those some kind of shower socks?"