setting font weight via rc

Using matplotlib 0.91.2 with the current development version of
ipython on Linux with no local matplotlibrc file, I have noticed that
setting the font weight via

rc('text',fontweight='bold')

or

rc('font',weight='bold')

changes the relevant rc parameter but doesn't affect the weight of the
displayed fonts used in the axes or titles. Specifying the weight in
matplotlibrc does work, however. Has anyone else observed this?

                             L.G.