diff --git a/src/regolith/regolith_depth_model.f90 b/src/regolith/regolith_depth_model.f90
index 6b424055..879375db 100644
--- a/src/regolith/regolith_depth_model.f90
+++ b/src/regolith/regolith_depth_model.f90
@@ -97,8 +97,9 @@ subroutine regolith_depth_model(user,domain,finterval,nflux,p)
          f    = 0.5_DP * dr * ( fmin + fmax )
          psum = psum + f   
       end do
-      psumfunc = exp(-1.0_DP * PI * psum * t)
-      if (psumfunc > epsilon(psum)) then
+      !psumfunc = exp(-1.0_DP * PI * psum * t)
+      psumfunc = -1.0_DP * PI * psum * t
+      if (psumfunc > log(epsilon(psum))) then
          p(2,i) = 1.0_DP - exp(-1.0_DP * PI * psum * t)
       else
          p(2,i) = 1.0_DP