google-app-engine - using protorpc message gives error: Excepted type absolute.path.to.MyMessage but found MyMessage

Question

After forming my ProtoRPC message, I get the error:

Expected type class 'protorpc.messages.MHistoryActivityViewMessage' for field items, found MHistoryActivityViewMessage\n body: u'Test Here'\n activity_id: 'WS-MHistory_ag9zfm1jYS1kZXJyaWNrLTFyGQsSEE1IaXN0b3J5QWN0aXZpdHkYsbyuBAw'

[...]

I have run across this issue many times where the expected type is 'absolute.path.to.MyMessage' but the found type is 'MyMessage'.

I'm stumped as to why I get this error. I have gotten this error many times. One workaround that sometimes works is moving the protorpc message definition higher up in the file seems.

Any hints or ideas?