A woman has learned – the hard way – not to lie. At least not when your sister is nearby.

Casey Sosnowski posted a perfectly posed picture right before her hike at Lake Okahumpka Park and Trail in Florida. The trees were lush, the trail was inviting and well-trodden — all the makings of an expertly crafted Instagram snap.

The only problem? It wasn’t true.

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Casey posed for the photo – with her arms out wide, holding a water bottle and dressed in athleisure wear – in her own backyard. She then posted the pic online, and tagged the sporty shot with the supposed hiking location. “Nature is the ultimate healer to all our problems,” she wrote in the caption, along with a hashtag reading “nature lovers.”

A screenshot of the original post shows it pulled in likes and comments from those thrilled by the adventurous picture.

However, Casey’s sister Carly wouldn’t let her get away with the lie.

On Twitter, Carly posted a screengrab of her sister’s Instagram post, along with a revealing behind-the-scenes shot of Casey posing for photos — not on some rural hiking trail, but in their backyard.

“My sister said she was going hiking.....this is our backyard,” Carly captioned the pictures.

The tweet quickly went viral, pulling in nearly 300K likes and over 40K retweets as of Thursday afternoon.

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Many commenters found the story hilarious, too.

Several were also impressed by the size of the backyard, saying that, actually, it looks a lot like a hiking spot.

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Casey responded to her sister, saying she felt “personally attacked,” before updating her Instagram picture to coyly suggest that, yes, this was her backyard.

“Did I go hiking? No. Is this my backyard?… Maybe,” she wrote, along with a winking-eye emoji.

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Just goes to show, you may be able to fool Instagram, but you can never fool your sister.