Using boolean global variable inside xquery doesn't work

I declared variable:
<variable name="boolVar" type="xsd:boolean"/>

Then I used xquery expression, like this:
<from expressionLanguage="urn:oasis:names:tc:wsbpel:2.0:sublang:xquery1.0">
if ($boolVar) then "trueValue" else "falseValue"
</from>

And I got:

[junit] Invocation#/home/joker/git/top/odetop-apache/APACHE_ODE_1.X/bpel-test/target/test-classes/bpel/2.0/TestXQueryExpression/test.properties#1: Unexpected final message exchange status; got FAULT:

{http://docs.oasis-open.org/wsbpel/2.0/process/executable}

selectionFailure | An exception occured while evaluating "

{OXPath10Expression null}

": Error while executing an XQuery expression: net.sf.saxon.trans.XPathException: No value supplied for required parameter $boolVar, expected RESPONSE

I did similar for string global var and it worked fine with expression like this:
<from expressionLanguage="urn:oasis:names:tc:wsbpel:2.0:sublang:xquery1.0">
if (xsd:boolean($stringVar)) then "trueValue" else "falseValue"
</from>

Attached is a test case for this.