A Dutch police station trying to help Muslim detainees face Mecca for their prayers painted arrows in cells pointing in the wrong direction.
The Segbroek police station in The Hague borrowed the idea of putting compass marks on ceilings from an Amsterdam hotel, the Dutch daily De Telegraaf reported on Friday.
Muslims pray five times a day, facing east in the direction of Mecca. But the arrows in Segbroek pointed west.
"This is a really gigantic, stupid blunder," a police spokesman told the De Telegraaf.
"The faulty compass marks have been immediately corrected. It is a mystery for us how this could have possibly happened."
All other police cells in the Dutch capital will soon get similar compass marks, the in-house newspaper of The Hague police said.
The Netherlands is home to 1 million Muslims out of a population of more than 16 million.
Immigration and the integration of newcomers have been hot topics since the rise and murder of populist politician Pim Fortuyn in 2002, who said the country could not absorb any more foreigners.