A Christie’s auction of alleged Jean-Michel Basquiat works is the subject a $1 million lawsuit filed on March 4 by the late artist’s sisters against the auction house. Jeanine Basquiat Henveaux and Lisan Basquiat claim that many of the artworks for sale are fake, but that Christie’s has inaccurately implied that they have been authenticated by the Basquiat estate.

The approximately 50-piece sale, running online through March 17, with a live auction March 6, comes from the collection of Alexis Adler, a former girlfriend of the artist. The two lived together in Adler’s Lower East Side apartment between 1979 and 1980.

Seven of the works up for auction were reviewed by the estate’s authentication committee before it disbanded in 2012. Only one piece, a radiator with the word “Milk” painted across it, was rejected (according to the sisters’ lawyer, the committee did not believe it was a work of art); the other six were ruled to be by the artist’s hand. Among the items up for sale are sketchbooks. prints, and collages, as well as less conventional works such as a door and a several sweatshirts painted by Basquiat.

Reportedly, the Christie’s catalogue states that the works are copyrighted by Basquiat’s estate, and the suit contends that such language could mislead collectors. Court papers filed by the siblings argue that “if the items in the catalog are not authenticated, they are virtually worthless.” The sisters claim that in February the estate denied Christie’s permission to reproduce work by Basquiat in its auction catalogue.