OASIS standard states that office:document-content should have a version attribute:

http://docs.oasis-open.org/office/v1.2/csprd03/OpenDocument-v1.2-csprd03-part1.html#__RefHeading__1417682_253892949

qtextodfwriter.cpp needs this one line (on line 781) to do this:

writer.writeAttribute(officeNS, QString::fromLatin1("version"), QString::fromLatin1("1.2"));