We study the sensitivity of the sound speed to relativistic corrections of
the equation of state (EOS) in the standard solar model by means of a helio
seismic forward analysis. We use the latest GOLF/SOHO data for l = 0, 1, 2,
3 modes to confirm that the inclusion of the relativistic corrections to t
he adiabatic exponent Gamma (1) computed from both OPAL and MHD EOS leads t
o a more reliable theoretical modelling of the innermost layers of the Sun.