full() returns false even if the circular buffer is full

Hi,
I have created a boost::circular_buffer using the default ctor.
Then I call set_capacity(100) and then I push_back() a thousand elements: the size() of the circular buffer is reported as 99 and thus the function full() always return false.

I think this is very misleading: my belief is that instead of having:

bool full() const BOOST_NOEXCEPT { return capacity() == size(); }

we should have:

bool full() const BOOST_NOEXCEPT { return capacity()-1 == size(); }

What am I missing?

Thanks,
Francesco