@objc closed enum in Swift possible?

In Xcode 11 I've created a binary xcframework written Swift. One of the public types that it defines is an enum, and it needs to be usable from Swift and Objecitve-C. So I added the @objc modifier like so:

@objc public enum MyEnum: Int {
    case aaa
    case bbb
}

I import the xcframework into a separate Swift project and have the following switch statement:

switch myEnum {
    case .aaa:
        break
    case .bbb:
        break
}

Unfortuntely compiling the switch statement produces this warning:

"Switch covers known cases, but 'MyEnum' may have additional unknown values."

If I were to define the enum in Objective-C instead of Swift, I would use NS_CLOSED_ENUM to ensure that there are no future cases, which would solve the Swift warning. But I don't know how to make a "closed enum" in Swift. Enums in Swift already are closed, but I think the @objc flag might be canceling that out in the interface.

Can this be solved? Thanks in advance.