ponyc: Segfault when trying to compile incorrect capabilities

trait T
    fun some() =>
        "Do nothing"

class TClass is T
    let _l: String
    new create(l: String) =>
         _l = consume l
    fun some() =>
        "Do nothing"

actor Act
    let _c: T iso
    new create(c: T iso) =>
        _c = consume c

actor Main
    new create() => 
        let c: T iso = TClass.create(l)
        let a: Act   = Act.create(c)

Adding a ^ to let c: T iso = ... causes a ponyc crash.