Recent sgml-common update (0.6.3-alt11 -> 0.6.3-alt13) breaks xmlto:

[builder@host Documentation]$ xmlto -m manpage-normal.xsl man git-add.xml
xmlto: input does not validate (status 3)
/usr/src/RPM/BUILD/git-1.6.3.2-alt2/Documentation/git-add.xml:2: warning: failed to load external entity "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"
D DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"
                                                                               ^
warning: failed to load external entity "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"
validity error : Could not load the external subset "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd"
Document /usr/src/RPM/BUILD/git-1.6.3.2-alt2/Documentation/git-add.xml does not validate

This bug blocks security update => Severity: blocker.