starts-with function error

[Myoungki Kim]

we make stylesheet with starts-with() function
but it couldnot error.

our stylesheet .
        .....
        <xsl:when test="starts-with(@HREF,'#')">

        </xsl:when>

Does sablotron support starts-with() function?

XSLTranslation: expr.cpp:1558: char * Expression::tostringCharPtr(): Assertion 
`(functor == EXF_ATOM) && (type == EX_STRING)' failed.
Aborted