diff --git a/cime_config/buildnml b/cime_config/buildnml
index bc8585d8..e56afca5 100755
--- a/cime_config/buildnml
+++ b/cime_config/buildnml
@@ -72,6 +72,8 @@ def _create_drv_namelists(case, infile, confdir, nmlgen, files):
     atm_mesh = case.get_value("ATM_DOMAIN_MESH")
     lnd_mesh = case.get_value("LND_DOMAIN_MESH")
     rof_mesh = case.get_value("ROF_DOMAIN_MESH")
+    ocn_mesh = case.get_value("OCN_DOMAIN_MESH")
+    wav_mesh = case.get_value("WAV_DOMAIN_MESH")
     config["samegrid_atm_lnd"] = (
         "true" if atm_mesh == case.get_value("LND_DOMAIN_MESH") else "false"
     )
@@ -85,6 +87,7 @@ def _create_drv_namelists(case, infile, confdir, nmlgen, files):
         "true" if atm_mesh == case.get_value("WAV_DOMAIN_MESH") else "false"
     )
     config["samegrid_lnd_rof"] = "true" if lnd_mesh == rof_mesh else "false"
+    config["samegrid_wav_ocn"] = "true" if ocn_mesh == wav_mesh else "false"
 
     # determine if need to set atm_domainfile
     scol_lon = float(case.get_value("PTS_LON"))
diff --git a/cime_config/config_component.xml b/cime_config/config_component.xml
index 667ab89a..9e58a0df 100644
--- a/cime_config/config_component.xml
+++ b/cime_config/config_component.xml
@@ -1415,7 +1415,9 @@
 
   <entry id="WAV2OCN_SMAPNAME">
     <type>char</type>
-    <default_value>idmap</default_value>
+    <values>
+      <value>unset</value>
+    </values>
     <group>run_domain</group>
     <file>env_run.xml</file>
     <desc>wav2ocn state mapping file</desc>
diff --git a/cime_config/namelist_definition_drv.xml b/cime_config/namelist_definition_drv.xml
index 8949fccb..8ee72422 100644
--- a/cime_config/namelist_definition_drv.xml
+++ b/cime_config/namelist_definition_drv.xml
@@ -2312,6 +2312,7 @@
       ocn to wav state mapping file for states
     </desc>
     <values>
+      <value samegrid_ocn_wav="true">idmap</value>
       <value>$OCN2WAV_SMAPNAME</value>
     </values>
   </entry>
@@ -2325,6 +2326,7 @@
       wav to ocn state mapping file for states
     </desc>
     <values>
+      <value samegrid_ocn_wav="true">idmap</value>
       <value>$WAV2OCN_SMAPNAME</value>
     </values>
   </entry>