diff --git a/python/extpar_era_to_buffer.py b/python/extpar_era_to_buffer.py
index dc5eb59a..58419e9f 100755
--- a/python/extpar_era_to_buffer.py
+++ b/python/extpar_era_to_buffer.py
@@ -144,7 +144,7 @@
 logging.info('')
 
 # calculate weights
-utils.launch_shell('cdo', '-f', 'nc4', lock, '-P', omp, f'genycon,{grid}',
+utils.launch_shell('cdo', '-f', 'nc4', lock, '-P', omp, f'genbil,{grid}',
                    tg.cdo_sellonlat(), raw_data_sst, weights)
 
 # regrid SST