xpath with predicates does not work

If I use Saxon 8.5.1 with XMLBeans the xpath expression with a simple predicate does not work.

I tried the example in the documentation on the website:

<?xml version="1.0" encoding="UTF-8"?>
<employees>
<employee>
<name>Fred Jones</name>
<address location="home">
<street>900 Aurora Ave.</street>
<city>Seattle</city>
<state>WA</state>
<zip>98115</zip>
</address>
<address location="work">
<street>2011 152nd Avenue NE</street>
<city>Redmond</city>
<state>WA</state>
<zip>98052</zip>
</address>
<phone location="work">(425)555-5665</phone>
<phone location="home">(206)555-5555</phone>
<phone location="mobile">(206)555-4321</phone>
</employee>
</employees>

The query I used was:
$this//phone[@location = 'work']

I got the error:
java.lang.RuntimeException: Trying XBeans path engine... Trying Saxon... FAILED on $this//phone[@location='work']
...stack trace ....

However, if I use Saxon 8.1.1 jar as stated in the page, it works OK.