diff --git a/src/tracer/MOM_generic_tracer.F90 b/src/tracer/MOM_generic_tracer.F90
index 5591e74d97..e998e3029c 100644
--- a/src/tracer/MOM_generic_tracer.F90
+++ b/src/tracer/MOM_generic_tracer.F90
@@ -584,13 +584,24 @@ subroutine MOM_generic_tracer_column_physics(h_old, h_new, ea, eb, fluxes, Hml,
                optics%nbands, optics%max_wavelength_band, optics%sw_pen_band, optics%opacity_band, &
                internal_heat=tv%internal_heat, frunoff=fluxes%frunoff, sosga=sosga)
     else
-      call generic_tracer_source(US%C_to_degC*tv%T, US%S_to_ppt*tv%S, rho_dzt, dzt, dz_ml, G%isd, G%jsd, 1, dt, &
+      ! tv%internal_heat is a null pointer unless DO_GEOTHERMAL = True,
+      ! so we have to check and only do the scaling if it is associated.
+      if(associated(tv%internal_heat)) then
+        call generic_tracer_source(US%C_to_degC*tv%T, US%S_to_ppt*tv%S, rho_dzt, dzt, dz_ml, G%isd, G%jsd, 1, dt, &
                G%US%L_to_m**2*G%areaT(:,:), get_diag_time_end(CS%diag), &
                optics%nbands, optics%max_wavelength_band, &
                sw_pen_band=G%US%QRZ_T_to_W_m2*optics%sw_pen_band(:,:,:), &
                opacity_band=G%US%m_to_Z*optics%opacity_band(:,:,:,:), &
                internal_heat=G%US%RZ_to_kg_m2*US%C_to_degC*tv%internal_heat(:,:), &
                frunoff=G%US%RZ_T_to_kg_m2s*fluxes%frunoff(:,:), sosga=sosga)
+      else
+        call generic_tracer_source(US%C_to_degC*tv%T, US%S_to_ppt*tv%S, rho_dzt, dzt, dz_ml, G%isd, G%jsd, 1, dt, &
+               G%US%L_to_m**2*G%areaT(:,:), get_diag_time_end(CS%diag), &
+               optics%nbands, optics%max_wavelength_band, &
+               sw_pen_band=G%US%QRZ_T_to_W_m2*optics%sw_pen_band(:,:,:), &
+               opacity_band=G%US%m_to_Z*optics%opacity_band(:,:,:,:), &
+               frunoff=G%US%RZ_T_to_kg_m2s*fluxes%frunoff(:,:), sosga=sosga)
+      endif
     endif
 
     ! This uses applyTracerBoundaryFluxesInOut to handle the change in tracer due to freshwater fluxes