Swift 4.2: Data equality changes?

Trying Alamofire's tests under Swift 4.2 mode and I'm getting some unexpected failures for some MultipartFormData tests that compare generated multipart data to a manually created instance. Despite the content on the Data values being identical (confirmed by base 64 string comparison), the XCAssertEqual fails. Have there been any changes to the Equatable conformance of Data?

Which version of Foundation?

Xcode 10 beta on 10.13.5.

More detail that may be relevant: the instance under test is loaded from a file saved to disk, the manually created instance from the utf8 representation of a String. Both are identical length and have the same base 64 representation. This occurs under Xcode 10 on macOS 10.13.5, running the tests of the macOS framework target.

I would file a radar in that case. I don't think the OS-Foundation's Data.== has changed recently.