diff --git a/src/MNH/set_mass.f90 b/src/MNH/set_mass.f90
index 6e6b816ed92609944d16415c63f3bbeccc3176f5..653ae79d5045b26ce9a47f1405647b02d550b083 100644
--- a/src/MNH/set_mass.f90
+++ b/src/MNH/set_mass.f90
@@ -572,6 +572,9 @@ ELSE
 ! ATmos: rho = P/ (R Tv)
  XRHODREFZ(:) = XP00/ (XRD* XTHVREFZ(:))
  ZTHVREF3D(:,:,:)=XTHVREFZ(2)
+   CALL COMPUTE_EXNER_FROM_GROUND(ZTHVREF3D,PZFLUX_MX,&
+          ZEXNSURF2D_MX,ZHEXNFLUX,ZHEXNMASS)
+
  XEXNTOP=SUM_DD_R2_ll(ZHEXNFLUX(IIB:IIE,IJB:IJE,IKE+1))/REAL(NIMAX_ll*NJMAX_ll)
  ZEXNTOP2D=ZHEXNFLUX(:,:,IKE+1)
  CALL COMPUTE_EXNER_FROM_TOP(ZTHVREF3D,XZZ,ZEXNTOP2D,ZHEXNFLUX,ZHEXNMASS)