diff --git a/src/tracer/MOM_generic_tracer.F90 b/src/tracer/MOM_generic_tracer.F90
index 131110e6b2..3865b95cef 100644
--- a/src/tracer/MOM_generic_tracer.F90
+++ b/src/tracer/MOM_generic_tracer.F90
@@ -512,7 +512,12 @@ subroutine MOM_generic_tracer_column_physics(h_old, h_new, ea, eb, fluxes, Hml,
     !
     g_tracer=>CS%g_tracer_list
     do
+! After ocean_BGC PR #20 has been merged in for a while, the following CPP macro can be removed.
+#ifdef _USE_OCEAN_BGC_PR20
       if (_ALLOCATED(g_tracer%trunoff) .and. (.NOT. g_tracer%runoff_added_to_stf)) then
+#else
+      if (_ALLOCATED(g_tracer%trunoff)) then
+#endif
         call g_tracer_get_alias(g_tracer,g_tracer_name)
         call g_tracer_get_pointer(g_tracer,g_tracer_name,'stf',   stf_array)
         call g_tracer_get_pointer(g_tracer,g_tracer_name,'trunoff',trunoff_array)
@@ -521,7 +526,10 @@ subroutine MOM_generic_tracer_column_physics(h_old, h_new, ea, eb, fluxes, Hml,
         runoff_tracer_flux_array(:,:) = trunoff_array(:,:) * &
                  US%RZ_T_to_kg_m2s*fluxes%lrunoff(:,:)
         stf_array = stf_array + runoff_tracer_flux_array
+! After ocean_BGC PR #20 has been merged in for a while, the following CPP macro can be removed.
+#ifdef _USE_OCEAN_BGC_PR20
         g_tracer%runoff_added_to_stf = .true.
+#endif
       endif
 
       !traverse the linked list till hit NULL