FlowExecutionHolder not available during portlet render phase

I am trying to get JSF and Spring Webflow working together in a portlet.
I ran into problems with my first page interaction. My first page has a link that initiates a flow. What I noticed is that the FlowNavigationHandler has the following code:

ViewSelection selectedView = flowExecution.start(createInput(context), context);
// set the starting view to render
FlowExecutionHolderUtils.getFlowExecutionHolder(facesContext).setViewSelection(selectedView);

In this process the FlowExecutionHolder is placed in the request.
Later, during the render phase the FlowPhaseListener beforePhase goes through the following:

if (FlowExecutionHolderUtils.isFlowExecutionRestored(event.getFacesContext())) {
prepareResponse(getCurrentContext(), FlowExecutionHolderUtils.getFlowExecutionHolder(event.getFacesContext()));
}

At this point an attempt is made to get the FlowExecutionHolder from the request. In a portlet scenario, however, the render is a separate request and the FlowExecutionHolder is no longer in the request.
As a result the view root does not get updated with the new view and the previous view gets redisplayed.