Derbyshire Police want to speak to anyone who saw a man expose himself to a 15-year-old girl in Chesterfield park.
It happened as the victim walked across Highfield Recreation Ground on Friday at around 3.20 in the afternoon.
He's described as white, in his 40s, around 5 foot 9 with short dark hair.
If you have information you can call on the police's non emergency number 101.
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