"No element in the source" when having to deal with namespaces

[MoonStorm]

The original file is a classic app.manifest:

<?xml version="1.0" encoding="utf-8"?>
<assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
    <security>
      <requestedPrivileges xmlns="urn:schemas-microsoft-com:asm.v3">
      </requestedPrivileges>
    </security>
  </trustInfo>
  [...]
</assembly>

I am getting an error No element in the source document matches '/_defaultNamespace:assembly/_defaultNamespace:trustInfo' when using the following transformation file:

<?xml version="1.0" encoding="utf-8" ?>
<assembly xmlns:xdt="http://schemas.microsoft.com/XML-Document-Transform" xmlns="urn:schemas-microsoft-com:asm.v1">
  <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
    <security>
      <requestedPrivileges xmlns="urn:schemas-microsoft-com:asm.v3">
        <requestedExecutionLevel level="requireAdministrator" uiAccess="true" xdt:Transform="Insert"/>
      </requestedPrivileges>
    </security>
  </trustInfo>
</assembly>

I tried with and without the xmlns attribute inside the transformation file.
Any help would be appreciated. Thanks.