WorkItemLinks collection always empty in PreviousRevision

[willstones]

I'm having a problem with the WorkItemLinks collection for a work item PreviousRevision. I have the following code which attempts to find either the current parent, or if there isn't one and it just got removed then the previous one.

Whenever I delete a link from a child to a parent the following code for the child work item never finds the old parent, and always logs "Work item X does not have a previous parent".

Any ideas?

        IWorkItemExposed parent = self.Parent;
        if(parent == null)
        {
            IWorkItemLinkExposed parentLink = self.PreviousRevision.WorkItemLinks.FirstOrDefault(wi => wi.LinkTypeEndImmutableName == WorkItemImplementationBase.ParentRelationship);
            if (parentLink != null)
            {
                parent = parentLink.Target;
            }
            else
            {
                logger.Log("Work item {0} does not have a previous parent", self.Id);
            }
        }