Export OxyPlots in collapsed ScrollViewer

I have added an OxyPlot inside of a ScrollViewer in WPF. This ScrollViewer is collapsed. I now want to export the plot (e.g. as a png). This only works if the plot has been displayed at least once (the ScrollViewer was visible at least once). When it has not been visible at least once the plot will not be exported.
How can I solve this problem?