src/jdk/nashorn/internal/runtime/options/OptionTemplate.java

@@ -150,10 +150,13 @@
             }
             break;
         case "timezone":
             this.defaultValue = TimeZone.getDefault().getID();
             break;
+        case "locale":
+            this.defaultValue = Locale.getDefault().toLanguageTag();
+            break;
         default:
             break;
         }
         return this.defaultValue;
     }