Invalid XML content error when Select unnest(xpath... is used

[rdee]

I have a text column named bid_xml in my table which has the following value:

<?xml version=1.0 encoding=UTF-8?>
<dpid:DpidDatabase xmlns:dpid=http://ddex.net/xml/dpid/11 xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance xsi:schemaLocation=http://ddex.net/xml/dpid/11 http://ddex.net/xml/dpid/11/dpid.xsd>
 <DpidOwner SequenceNumber=1>
  <DPID>PADPIDA2006111001O</DPID>
  <CompanyName>234AG</CompanyName>
  <Address>Riedtlistrasse 23, Zürich, 8006, CH</Address>
 </DpidOwner>
 <DpidOwner SequenceNumber=2>
  <DPID>PADPIDA2007011501Q</DPID>
  <CompanyName>OpenIMP</CompanyName>
  <Address>8-10 Rhoda Street, London, E2 7EF, UK</Address>
 </DpidOwner>
 <DpidOwner SequenceNumber=3>
  <DPID>PADPIDA2007040501K</DPID>
  <CompanyName>The Harry Fox Agency</CompanyName>
  <Address>711 Third Avenue, 8th Floor, New York, 10017, USA</Address>
 </DpidOwner>
</dpid:DpidDatabase>

Execute query:

SELECT 
  unnest((xpath('/dpid:DpidDatabase/DpidOwner',  int_config.ddex_dpid_xml_20190828.big_xml::xml,ARRAY[ARRAY['dpid', 'http://ddex.net/xml/dpid/11']]))) AS SequenceNumber   
  ,unnest((xpath('/dpid:DpidDatabase/DpidOwner/DPID',  int_config.ddex_dpid_xml_20190828.big_xml::xml,ARRAY[ARRAY['dpid', 'http://ddex.net/xml/dpid/11']]))) AS DPID
  ,unnest((xpath('/dpid:DpidDatabase/DpidOwner/CompanyName',  int_config.ddex_dpid_xml_20190828.big_xml::xml,ARRAY[ARRAY['dpid', 'http://ddex.net/xml/dpid/11']]))) AS CompanyName 
  ,unnest((xpath('/dpid:DpidDatabase/DpidOwner/Address',  int_config.ddex_dpid_xml_20190828.big_xml::xml,ARRAY[ARRAY['dpid', 'http://ddex.net/xml/dpid/11']]))) AS Address
FROM int_config.ddex_dpid_xml_20190828

Error displayed:

ERROR: invalid XML content
  Detail: line 1: XML declaration allowed only at the start of the document
<?xml version=1.0 encoding=UTF-8?>
        ^
1 statement failed.