diff --git a/mo_grav_drain.f90 b/mo_grav_drain.f90
index 325a2450e5cb77d1868b7d3e984cb7d37010c57d..68e23bbcb9ab2ba53545db31677adee41671e9e7 100644
--- a/mo_grav_drain.f90
+++ b/mo_grav_drain.f90
@@ -91,7 +91,7 @@ CONTAINS
     REAL(wp)                                     :: heat_loss             !< Amount of heat transported from the ice [J]
     INTEGER                                      :: k,kk
     REAL(wp), DIMENSION(Nlayer+1,Nlayer+1), INTENT(inout),OPTIONAL :: fl_brine_bgc 
-	REAL(wp),                      INTENT(out)   :: grav_heat_flux_down, grav_heat_flux_up
+    REAL(wp),                      INTENT(out)   :: grav_heat_flux_down, grav_heat_flux_up
 
     ray_mini       = ray_crit!Arises from the optimization of the r
     heat_loss      = 0._wp