IDE can't find declaration of element in xsl file

Question

I work on an old java 5 project but I can't run it. Before I try to run it, Eclipse (Neon.2 Release 4.6.2) indicate to me this error:

cvc-elt.1 cannot find the declaration of element xsl:stylesheet

Here, the xml code which is in error:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:fo="http://www.w3.org/1999/XSL/Format" version="1.0">
    <xsl:output method="xml" encoding="UTF-8" />
    ....
    ....

Eclipse indicate the error on this line (line 3):

 xmlns:fo="http://www.w3.org/1999/XSL/Format" version="1.0">

I understand the error but I don't know how to resolve it. What can I do to resolve it?

Answer 1

I get this error when there are spaces in the filename. Once removed, the error no longer appears. I am not using the same version of Eclipse though.