I'm trying to use kotlin contracts but I'm getting an unresolved reference when I build the project. the class I have looks like this:

sealed class Foo {
    fun isFooOne(): Boolean {
        contract {
            returns(true) implies (this@Foo is FooOne)
            returns(false) implies (this@Foo is FooTwo)
        }
        return this is FooOne
    }

    data class FooOne(val valueOne: String) : Foo()
    data class FooTwo(val valueTwo: String, val bar: String) : Foo()
}

This is defined in a share kotlin multiplatform project. I'm able to use this in another module(android project) like so:

val foo = getFoo()
if (foo.isFooOne()) {
    val fooValue = foo.valueOne
} else {
    val fooBar = foo.bar
}

The ide doesn't give any error but when I build the project it say

foo.bar

is unresolved at

val fooBar = foo.bar

. Not sure what I'm missing here...any insight would be appreciated. Thanks