Compiling the expression //. | / throws a java.util.NoSuchElementException As near as I can figure the problem occurs in JaxenHandler.endUnionExpr when the second call to pop() is made. public void endUnionExpr(boolean create) throws JaxenException { if ( create ) { Expr rhs = (Expr) pop(); // FIXME this next line is dying with a NoSucElementException // with the XPath expression //. | / Expr lhs = (Expr) pop(); push( getXPathFactory().createUnionExpr( lhs, rhs ) ); } } Possibly however this is just a symptom of an earlier bug. The equivalent expression / | //. does not cause a problem.