I broke Ms Dynamics CRM 2013 today

So I have a custom workflow activity that has an output of a custom reference, something like this:

[Output("ClientRecord")]
[ReferenceTarget("new_clientrecord")]
public OutArgument<EntityReference> ClientRecord { get; set; }

And like idiot I did this:

ClientRecord.Set(executionContext, ClientRecordEntity);

where ClientRecordEntity is an Entity and not an EntityReference.

Running the Dialog that contained this workflow activity, resulted in a very, very long wait and after that, 503 for absolutely everybody using the dev environment.

A proud day, today

I broke CRM.