Boo.Lang.Hash bug?

I have the following code: for (var k in resourceIcons) Debug.Log(resourceIcons[k.Key]);

where resourceIcons is a hash. This gives me a MissingFieldException: Field System.MonoType.resourceIcon not found.

This exception is being thrown from line 2, so it's trying to dynamically resolve a non-existent field. However that should be impossible in this case since I'm enumerating the keys of the hash. Can someone shed some light on this?