How to avoid duplicating column headers in nlog CSVLayout?

Question

I'm using a nlog's CSV layout file for data logging.

<target xsi:type="File" [...]>
  <layout xsi:type="CSVLayout">
    <column name="Value1" layout="${event-context:item=Value1}"/>
    [...]

I'm getting column headers appended to the file every time I run the logging application. Is there a way to only get the column headers created when a new log file is created?

Thanks