According to type-B materialism, the corresponding phenomenal and physical concepts are distinct concepts of the same properties. This view is very controversial because of the fact that phenomenal concepts, along with physical concepts, refer non contingently. I discuss three main arguments to the effect that phenomenal concepts cannot refer to physical properties non contingently. I argue that the most challenging is the modal argument. According to this argument, the idea that phenomenal concepts refer to physical properties non contingently is unacceptable, because it leads to the unacceptable view that psychophysical identity statements are both true a posteriori and primarily necessary. I argue that we do not have a satisfactory response to that argument.