Marker-mid orientation wrong on closed paths

[fskpf]

Compare the marker orientations in this example. Note how the orientation is wrong where the path and polygon is closed:

<svg viewBox="0 0 400 400" 
  xmlns="http://www.w3.org/2000/svg" width="400" height="400">
  <defs>
    <marker id="arrow" viewBox="0 0 10 10" refX="5" refY="5" markerWidth="16" markerHeight="16" orient="auto-start-reverse">
      <path d="M 0 0 L 10 4 L 10 6 L 0 10 z" />
    </marker>
  </defs>

  <path d="M 150,80 L 200,80 L 200,180 z" stroke="gray" fill="none"  marker-start="url(#arrow)" marker-mid="url(#arrow)" marker-end="url(#arrow)"/>

  <polygon points="275,200 325,125 325,175 375,100" fill="none" stroke="gray" marker-start="url(#arrow)" marker-mid="url(#arrow)" marker-end="url(#arrow)" />
</svg>