diff --git a/vasl_templates/webapp/static/main.js b/vasl_templates/webapp/static/main.js
index 9fa37f6..476d92a 100644
--- a/vasl_templates/webapp/static/main.js
+++ b/vasl_templates/webapp/static/main.js
@@ -701,6 +701,15 @@ function on_player_change( player_no )
     $( "#ob_ordnance-sortable_" + player_no ).sortable2( "delete-all" ) ;
     $("input[name='OB_ORDNANCE_WIDTH_"+player_no+"']").val( "" ) ;
 
+    // enable/disable the "add vehicle/ordnance" buttons
+    function update_add_vo_button( vo_type ) {
+        $( "#ob_"+vo_type+"-add_"+player_no ).button(
+            gVehicleOrdnanceListings[vo_type][player_nat] ? "enable": "disable"
+        ) ;
+    }
+    update_add_vo_button( "vehicles" ) ;
+    update_add_vo_button( "ordnance" ) ;
+
     // update the ROAR info panel
     set_roar_scenario( $("input[name='ROAR_ID']").val() ) ;
 }
diff --git a/vasl_templates/webapp/tests/test_vehicles_ordnance.py b/vasl_templates/webapp/tests/test_vehicles_ordnance.py
index 6160021..b95c8ba 100644
--- a/vasl_templates/webapp/tests/test_vehicles_ordnance.py
+++ b/vasl_templates/webapp/tests/test_vehicles_ordnance.py
@@ -422,19 +422,17 @@ def test_common_vo( webapp, webdriver ):
         select_tab( "ob1" )
         for vo_type in ("vehicles","ordnance"):
 
-            # get the vehicles/ordnance
-            last_warning_marker = set_stored_msg_marker( "_last-warning_" )
+            # check if the nationality has any vehicles/ordnance
             elem = find_child( "#ob_{}-add_1".format( vo_type ) )
-            elem.click()
-            last_warning = get_stored_msg( "_last-warning_" )
             if nat in ["thai","indonesian","anzac","burmese","filipino"]: # nb: these are in the BFP extension
-                assert last_warning.startswith( "There are no" )
+                assert not elem.is_enabled()
                 continue
             elif nat == "kfw-cpva" and vo_type == "vehicles":
-                assert last_warning.startswith( "There are no" )
+                assert not elem.is_enabled()
                 continue
-            else:
-                assert last_warning == last_warning_marker
+            elem.click()
+
+            # get the vehicles/ordnance
             vo_entries = find_children( "#select-vo .select2-results li" )
             vo_entries = [ get_vo_entry(e) for e in vo_entries ]
             click_dialog_button( "Cancel" )