The present invention relates to the xinafoate salt of N4-[(2,2-difluoro-4H-benzo[1,4]oxazin-3-one)-6-yl]-5-flu-oro-N2-[3-(methylaminocarbonylmethylene oxy)phenyl]-2,4-pyrimidinediamine.This compound is a suitable drug substance andis useful in the treatment of conditions including asthma.