2 Dimensional Convolution using RooFit

ROOT Version: 5.24
RooFit Version: 3.0
Machine: x86, CentOs
Hello, I am trying to convolute one of the dimensions of a 2-dimensional pdf in RooFit (as per page 41 of the RooFit users' manual). It works fine (although very slow) when using numerical convolution through the RooNumConvPdf class.

However, when I try it using the FFT convolution scheme via the RooFFTConvPdf class, I get strange results: The convolution variable (x in the macro) is handled correctly, but the non-convoluted variable (y in the macro) ends up with a flat, uniform distribution.

I've confirmed this with a more recent version of ROOT (5.31) and RooFit (3.17). Is there any way to preserve the distribution in the non-convoluted variable?

Thanks,

     -Bill