log4j2 NoSQLAppender for MongoDB4 capped config not work

log4j2 NoSQLAppender for MongoDB4, log4j2.xml capped config not work.MongoDb Collection status capped is false.

<Appenders>
<NoSql name="MongoDbAppender">
  <MongoDb4 
    connection="mongodb://localhost:${sys:MongoDBTestPort:-27017}/testDb.testCollection" 
    capped="true" 
    collectionSize="4096"/>
</NoSql>