verimageurl loads with an empty source modx 0.9.6 and eform 1.4

<fieldset class="spam">
      <legend>Spamschutz</legend>
      <p>Antispam-Code:<br />
      <img src="[+verimageurl+]" alt="verification code" border="1" /></p>
      <p><label accesskey="c" for="vericode">Anitspam-Code hier eingeben*</label> <input type="text" name="vericode" size="20" id="vericode" /></p>
    </fieldset>