Namespace in xml to xml

I want to transform my xml into tei xml via xslt.

My xml has no namespace. The output (i.e., tei xml) needs to be in the tei namespace.

If in the xsl file I have xmlns:tei="http://www.tei-c.org/ns/1.0" in the xsl:stylesheet declaration, I get the element in the output, while I want . 

This can be achieved either by having an explicit in the xsl template, or by having xmlns="http://www.tei-c.org/ns/1.0" instead of xmlns:tei="http://www.tei-c.org/ns/1.0" in the xsl:stylesheet element. However,
in both cases the child of in  the output, i.e., , will now have xmlns="", an empty namespace.

No solution so far.