Unexpected rule is fired when a constraint contains a function and multiple "=="

Issue

• Unexpected rule is fired when a constraint contains a function and multiple "==". For example,

rule R1
    when
        $p: Person(myFunction("param == 10", age) == 1)
    then
end
rule R2
    when
        $p: Person(myFunction("param == 20", age) == 1)
    then
end

When I insert a fact which should match only R1, both rules (R1 and R2) are fired.