XPC method not invoked with NSArray of NSValues as parameter

Question

I have an XPC service compiled 32-bit for OS-X. One of it's methods takes a single argument as a parameter, and calls a given block back on the main process.

This block takes 3 NSStrings and an NSArray that's supposed to contain NSValues solely. Each NSValue object holds an NSRect.

For some reason, the given block is not being called when the NSArray is not nil. If instead of holding NSValues I let the array hold NSStrings, the block is being called correctly.

I'm not sure how to approach this, as there is no apparent reason for this to happen. According to the apple documentation, NSValue does conform to NSSecureCoding.

I even tried whitelisting the NSValue class (this shouldn't really be needed) using:

NSSet *readerSelectionClasses =
[NSSet setWithObjects:[NSArray class], [NSValue class], nil];

[newConnection.exportedInterface setClasses:readerSelectionClasses forSelector:@selector(MyMethod:WithReply:) argumentIndex:3 ofReply:YES];

This doesn't seem change anything.

Any idea how to pass the NSArray? I guess I could format all NSRects to NSStrings, and pass an array of NSStrings, which I know works, but this would lead to a performance decrease I would rather avoid.