TreeBagger Cost input argument is not recognized

A similar question was already posted, but without satisfying replies.

The TreeBagger function seems not to catch the Cost name-pair input argument, as it should do following the documentation. Even if I specify the matrix cost I need (I have unbalanced classes), in the output structure the cost matrix is the default one [0 1;1 0].

Does anyone know how to solve this issue?

Thank you for your help!