Issue with function:count()

[Vission01]

Given an example XML:
<object> <element> <node>x</node> </element> <element> <node>x</node> </element> <element> <node>x</node> </element> <element> <node>y</node> </element> <element> <node>x</node> </element> </object>

This seems to work:

count(object/element[node='x'])

This does not:

object/count(element[node='x'])

You get: Error evaluating XPath

This works in other XPath tools, such as:
https://www.freeformatter.com/xpath-tester.html#before-output