diff --git a/gen_weights.sh b/gen_weights.sh
index a851c74de514674fec6b7d053aaf37d6d33f3884..a3572d86c9ecd246721cdce8eeb337d535cfe5f4 100755
--- a/gen_weights.sh
+++ b/gen_weights.sh
@@ -7,4 +7,8 @@ grid_label=O
 grid_name=icon_grid_${grid_id}_${grid_refinement}_${grid_label}
 zoom=13
 
-cdo -P 4 -gennn,hpz${zoom} -const,0,${grids_folder}/icon_grid_${grid_id}_${grid_refinement}_${grid_label}.nc weights_${grid_refinement}_${grid_label}_hpz${zoom}.nc
+if [[ $grid_label == "O" ]]; then
+  cdo -P 4 -gennn,hpz${zoom} -setrtomiss,0,2 -select,name=cell_sea_land_mask ${grids_folder}/icon_grid_${grid_id}_${grid_refinement}_${grid_label}.nc weights_${grid_refinement}_${grid_label}_hpz${zoom}.nc
+else
+  cdo -P 4 -gennn,hpz${zoom} -const,0,${grids_folder}/icon_grid_${grid_id}_${grid_refinement}_${grid_label}.nc weights_${grid_refinement}_${grid_label}_hpz${zoom}.nc
+fi