I'm writing a TeX-noweb document. I compile it with

noweave -tex -filter "elide comment:*" texcode.nw > documentation.tex

but when I try to compile the resulting file with

xetex -halt-on-error documentation.tex

I obtain the following error message

! Undefined control sequence.
<argument> ...on}\endmoddef \nwstartdeflinemarkup 
                                              \nwenddeflinemarkup

It seems that \nwenddeflinemarkup is not recognized. If i delete from the document all the sequences

\nwstartdeflinemarkup\nwenddeflinemarkup

the document compile without exceptions.

What can be the problem?