Missing space in formatted output conversion

A leading space is missing in the output of
   
  mpl.text(1, 1, '% .3f' % 1.234)

if used within the TeX backend. Whereas it is not
missing in the plain non-TeX backend.
Here is an example:

  import pylab as mpl
  #mpl.rcParams['text.usetex'] = False
  mpl.rcParams['text.usetex'] = True

  mpl.plot([1,3,2])
  mpl.text(1, 2.0, '% .3f' % 1.234)
  mpl.text(1, 1.9, '% .3f' % -1.234)
  mpl.show()

Ciao
Andreas