Four eighth note beamed when first eighth note looks like a half note

[Knute Snortum]

I have a situation that seems like it would be straightforward.  I
want four eighth notes beamed with the first eighth looking like a
half note.  I thought I could just do this:

{ b2*1/4[ b'8 b' b'] }

But that code doesn't attach the beam to the first note and produces
two warnings:

warning: stem does not fit in beam
warning: beam was started here

What am I doing wrong?

--
Knute Snortum