Ctreating DNXHR 12Bit MXF files not working in avid

I rendered out DNXHR 12 bit MXF files and Tried to load them into the latest version of Avid 8.3.1 (UHD Project) and avid complained they were an Unsupported “unsupported pixel format”. Cortex will load the files back into it fine, can someone confirm the that this is true or if there is a fix or work around.

DNxHR 12 bit files are only going to load properly in Media Composer 8.4.