The call in my application to ID3D11DeviceContext::ClearDepthStencilView (with D3D11_CLEAR_STENCIL as the flag) doesn't clear the stencil buffer. Stencil operations work fine, but the stencil buffer is cleared to 0xff after every buffer swap regardless of the passed value. What could be causing this?

EDIT: The 0xff is from another call to the same function earlier in the code, but then why does that call work and the other doesn't?