prawn-svg: SVG vector image: arrow-head not displayed

Hi!

The following sample.rb:

require 'rubygems'
require 'prawn'
require 'prawn-svg'

Prawn::Document.generate("arrows.pdf") do |pdf|
  pdf.svg File.read("arrows.svg"), :at => [0, 600], :width => 500
end

does not display the arrow-heads in the SVG image.

Source of the SVG arrows.svg (for copy-pasting):

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!-- Created with Inkscape (http://www.inkscape.org/) -->

<svg
   xmlns:dc="http://purl.org/dc/elements/1.1/"
   xmlns:cc="http://creativecommons.org/ns#"
   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
   xmlns:svg="http://www.w3.org/2000/svg"
   xmlns="http://www.w3.org/2000/svg"
   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
   width="200"
   height="200"
   id="svg2"
   version="1.1"
   inkscape:version="0.48.5 r10040"
   sodipodi:docname="New document 1">
  <sodipodi:namedview
     id="base"
     pagecolor="#ffffff"
     bordercolor="#666666"
     borderopacity="1.0"
     inkscape:pageopacity="0.0"
     inkscape:pageshadow="2"
     inkscape:zoom="1.979899"
     inkscape:cx="131.67459"
     inkscape:cy="71.158705"
     inkscape:document-units="px"
     inkscape:current-layer="layer1"
     showgrid="false"
     inkscape:window-width="1680"
     inkscape:window-height="948"
     inkscape:window-x="0"
     inkscape:window-y="31"
     inkscape:window-maximized="1" />
  <defs
     id="defs4">
    <marker
       style="overflow:visible;"
       id="Arrow1Lend"
       refX="0.0"
       refY="0.0"
       orient="auto"
       inkscape:stockid="Arrow1Lend">
      <path
         transform="scale(0.8) rotate(180) translate(12.5,0)"
         style="fill-rule:evenodd;stroke:#000000;stroke-width:1.0pt;"
         d="M 0.0,0.0 L 5.0,-5.0 L -12.5,0.0 L 5.0,5.0 L 0.0,0.0 z "
         id="path3762" />
    </marker>
    <marker
       style="overflow:visible"
       id="Arrow1Lend-3"
       refX="0"
       refY="0"
       orient="auto"
       inkscape:stockid="Arrow1Lend">
      <path
         transform="matrix(-0.8,0,0,-0.8,-10,0)"
         style="fill-rule:evenodd;stroke:#000000;stroke-width:1pt"
         d="M 0,0 5,-5 -12.5,0 5,5 0,0 z"
         id="path3762-1"
         inkscape:connector-curvature="0" />
    </marker>
    <marker
       style="overflow:visible;"
       id="Arrow1LendK"
       refX="0.0"
       refY="0.0"
       orient="auto"
       inkscape:stockid="Arrow1LendK">
      <path
         transform="scale(0.8) rotate(180) translate(12.5,0)"
         style="stroke:#ff0000;stroke-width:1.0pt;fill:#ff0000;fill-rule:evenodd"
         d="M 0.0,0.0 L 5.0,-5.0 L -12.5,0.0 L 5.0,5.0 L 0.0,0.0 z "
         id="path4230" />
    </marker>
  </defs>
  <metadata
     id="metadata7">
    <rdf:RDF>
      <cc:Work
         rdf:about="">
        <dc:format>image/svg+xml</dc:format>
        <dc:type
           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
        <dc:title></dc:title>
      </cc:Work>
    </rdf:RDF>
  </metadata>
  <g
     transform="translate(0,-852.36218)"
     id="layer1"
     inkscape:groupmode="layer"
     inkscape:label="Layer 1">
    <path
       transform="translate(0,852.36218)"
       inkscape:connector-curvature="0"
       id="path2985"
       d="M 26.263966,144.94669 122.22846,94.439059"
       style="fill:none;stroke:#000000;stroke-width:1px;stroke-linecap:butt;stroke-linejoin:miter;stroke-opacity:1;marker-end:url(#Arrow1Lend)" />
    <path
       inkscape:connector-curvature="0"
       id="path2985-7"
       d="M 40.406101,953.8723 136.3706,903.36467"
       style="stroke-linejoin:miter;marker-end:url(#Arrow1LendK);stroke-opacity:1;stroke:#ff0000;stroke-linecap:butt;stroke-width:1px;fill:#ff0000" />
  </g>
</svg>

(Issue originally filed at asciidoctor-pdf ref, which uses prawn)