SOAP method progressWorkFlowAction shows different behaviour in JIRA 3.13.3 compared to 3.13.2

We are currently investigating an issue with the JIRA SOAP interface, and our conclusions are as follows:-

With Jira 3.13.2, the SOAP method progressWorkFlowAction can be used to resolve an issue without providing a value for the Resolution field. The default value is then applied to the Resolution field, which in our case is "Fixed".

However, with Jira 3.13.3, this no longer appears to be the case, and a value for the Resolution field has to be provided when resolving an issue through the SOAP interface, even though there is a default value.

There appears to be no reference to this change in functionality in the release notes, and we would like to understand if this is an intentional change, which will require us to update our own code to work around this change in behaviour.

Ideally, we would like progressWorkFlowAction to work the same through the web interface and the SOAP interface, i.e. if no Resolution is provided, then the default is taken.