A man who decided to rub his crotch on straphanger this week got busted immediately when the victim he picked turned out to be a plainclothes NYPD detective.

Cops say that at around 9:05 a.m on Thursday, Felipe Mondragon repeatedly rubbed his groin area on the officer's right thigh, shortly after a 6 train both of them were riding left Union Square. The undercover officer, accompanied by her partner and a sergeant, arrested Mondragon, and got off the train at the 23rd Street station, an NYPD spokesperson told Gothamist. Mondragon, a 52-year-old from Jackson Heights, was charged with forcible touching and sex abuse. Mondragon has two prior arrests, which are sealed.

A similar incident took place on an uptown 6 train in May, when a 38-year-old man was arrested right after he rubbed his crotch against the thigh of Jennifer Rosario, a plainclothes detective.