Museum curator Susanne Meyer-Buser noticed that a 1944 photograph of the art displayed the canvas differently.
A painting by Dutch abstract painter Piet Mondrian has been hanging upside down for 77 years, says a curator at the German museum.
A large retrospective of the avant-garde artist's work went on display Saturday at the Kunstsammlung museum in Dusseldorf, and one of the pieces on show is "New York City 1", painted in 1941.
But as she prepared for the exhibition, curator Susanne Meyer-Buser discovered the painting had been presented to the public rather differently from how it was perhaps intended to be on show.
"In a photo from 1944, I saw that the canvas was the other way around on an easel. It intrigued me," Meyer-Buser told German daily Suddeutsche Zeitung.
The painting, consisting of several lines in blue, red and yellow intersecting at right angles, was then displayed shortly after in the wrong way at MoMA in New York, the curator said.
It was then transferred to the Dusseldorf museum in 1980 and put on show in the same way.
The error could have been made because "the painting doesn't have a signature", according to Meyer-Buser.
The decision to present the work in the manner it has been for decades was probably determined by " the artist's name inscribed on the back of the frame by the administrator of the (artist's estate)" at the time of Mondrian's death in 1944.
Mondrian, born in 1872, was a noted exponent of the 1920s abstract art movement known as "De Stijl" and was one of the most influential figures in modern art in the 20th century.
In 1940, he moved to New York where the skyscrapers and layout of the city would inspire his horizontal lines. He died in New York in 1944.
His most famous artwork is "Victory Boogie Woogie", considered one of the most important artworks of the 20th century.