A man who snuck a bag of cannabis into prison in his nose 18 years ago has finally had the dried-up weed removed from his nasal cavity, according to a new case report published in British Medical Journal Case Reports.

It is the “first reported case of a prison-acquired marijuana-based rhinolith,” also known as a nose stone, said a team led by Murray Smith, a physician at Westmead Hospital in Sydney, Australia.

“During a prison visit, the patient’s girlfriend supplied him with a small quantity of marijuana, inside a rubber balloon,” Smith and his colleagues note in the report, which is entitled “a nose out of joint.”

The patient, who is now 48, slipped the package into his right nostril, and was able to hide it from prison guards this way. But when he tried to retrieve it, he accidentally lodged the pot deeper into his nasal cavity and assumed that he had unknowingly swallowed it at some point.

As it turns out, the nose weed never quite made it to the man’s throat, and instead developed into a gray calcified lesion measuring 19 by 11 millimeters. Rhinoliths are uncommon, but have been known to form around blood clots or foreign objects that have entered the nasal cavity, such as beads, cotton, or plant matter.

The patient with the marijuana-based rhinolith said that he had a history of nasal obstruction and frequent sinus infections, but the source of those symptoms wasn’t noticed until he sought treatment for painful headaches. A CT scan of his brain revealed the “rubber capsule containing degenerate vegetable/plant matter,” as Smith’s team describe it, which doctors removed under general anaesthesia.

“At a three-month follow-up, the patient reported complete resolution of his sinonasal symptoms,” the authors said.

While this is the first instance of a marijuana-based rhinolith, a 2007 study reported that a 21-year-old man had a “hardened mixture of codeine and opium wrapped in a small sheet of nylon” removed from his nose.