analogWrite for B4 and B5 not working?

I just checked up on this, and it's one of the STM32F1's slightly crazy arrangements.

If you do the following, it should all work:

analogWrite(B4, 0.5, {freq:10});
poke32(0x40010004, peek32(0x40010004)&(~0x7000C00)|0x4000800)

I'll try and fix it for the next version...