When i transform (xsltproc) this banal xml

--- begin "a.xml" ---
<?xml version="1.0"?>
  <root/>
--- end "a.xml" ---

with this simple xslt

--- begin "b.xslt" ---
<?xml version="1.0" encoding="utf-8"?>

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="root">
<xsl:variable name="new_element_name" select="'new_root'"/>
<xsl:element name="{$new_element_name}"/>
</xsl:template>

<xsl:template match="no_element">
      <xsl:if test="1"> <xsl:element name="no_new_element">
          <xsl:if test="0"/></xsl:element>
           </xsl:if>
  </xsl:template>

</xsl:stylesheet>
--- end "b.xslt" ---

and i use the latest windows (Zlatkovic) versions of libxml2 (2.6.32+) and libxslt/xsltproc (1.1.23+), i obtain the following error

--- begin output with libxslt2 2.6.32+ --- 
runtime error: file b.xslt line 7 element element
Variable 'new_element_name' has not been declared.
xmlXPathCompiledEval: evaluation failed
runtime error: file b.xslt line 7 element element
xsl:element: The attribute 'name' is missing.
no result for a.xml
--- end output with libxslt2 2.6.32+ ---

   Apparently this problem is a 'libxml2' problem because when i use the preceding windows version (2.6.30), the problem disappear.
   On the contrary, i obtain the same error, with libxml2 2.6.32+, even with libxslt/xsltproc 1.1.22, 1.1.19, 1.1.17, 1.1.16 and 1.1.15+.

--- begin output with libxslt2 2.6.30 ---
<?xml version="1.0"?>
<new_root/>
--- end output with libxslt2 2.6.32+ ---

The eccentric part of this problem is that it disapper even if you delete or modify (the indentation spaces are significant) the unused (?) "no_element" template.

I add the verbose outputs ("xsltproc --verbose b.xslt a.xml")

--- begin verbose output with libxslt2 2.6.32+ ---
creating dictionary for stylesheet
reusing dictionary from b.xslt for stylesheet
xsltParseStylesheetProcess : found stylesheet
xsltPrecomputeStylesheet: removing ignorable blank node
xsltCompilePattern : parsing 'root'
xsltCompilePattern : parsed root, default priority 0.000000
added pattern : 'root' priority 0.000000
xsltCompilePattern : parsing 'no_element'
xsltCompilePattern : parsed no_element, default priority 0.000000
added pattern : 'no_element' priority 0.000000
parsed 2 templates
Resolving attribute sets references
Creating sub-dictionary from stylesheet for transformation
Registered 0 modules
reusing transformation dict for output
Registering global variables
Registering global variables from b.xslt
xsltProcessOneNode: no template found for /
xsltProcessOneNode: applying template 'root' for root
Registering variable 'new_element_name'
Building variable new_element_name select 'new_root'
Evaluating variable 'new_element_name'
Object is a string : new_root
Lookup variable 'new_element_name'
global variable not found new_element_name
variable not found 'new_element_name'
runtime error: file b.xslt line 7 element element
Variable 'new_element_name' has not been declared.
xmlXPathCompiledEval: evaluation failed
xsltEvalXPathString: returns (null)
xsltEvalAttrValueTemplate: {$new_element_name} returns (null)
runtime error: file b.xslt line 7 element element
xsl:element: The attribute 'name' is missing.
freeing transformation dictionary
no result for a.xml
freeing dictionary from stylesheet
--- end verbose output with libxslt2 2.6.32+ ---

--- begin verbose output with libxslt2 2.6.30 ---
creating dictionary for stylesheet
reusing dictionary from b.xslt for stylesheet
xsltParseStylesheetProcess : found stylesheet
xsltPrecomputeStylesheet: removing ignorable blank node
xsltCompilePattern : parsing 'root'
xsltCompilePattern : parsed root, default priority 0.000000
added pattern : 'root' priority 0.000000
xsltCompilePattern : parsing 'no_element'
xsltCompilePattern : parsed no_element, default priority 0.000000
added pattern : 'no_element' priority 0.000000
parsed 2 templates
Resolving attribute sets references
Creating sub-dictionary from stylesheet for transformation
Registered 0 modules
reusing transformation dict for output
Registering global variables
Registering global variables from b.xslt
xsltProcessOneNode: no template found for /
xsltProcessOneNode: applying template 'root' for root
Registering variable 'new_element_name'
Building variable new_element_name select 'new_root'
Evaluating variable 'new_element_name'
Object is a string : new_root
Lookup variable 'new_element_name'
xsltEvalXPathString: returns new_root
xsltEvalAttrValueTemplate: {$new_element_name} returns new_root
freeing transformation dictionary
<?xml version="1.0"?>
<new_root/>
freeing dictionary from stylesheet
--- end verbose output with libxslt2 2.6.30 ---