x86-64 not faulting when CS.L = 1 and CS.D = 1

In a UEFI application I accidentally created a code segment descriptor where both the L and D bits were 1. This is supposed to generate a GP fault (e.g. see page 2942 of https://software.intel.com/sites/default/files/managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdf). When running with KVM a fault did indeed occur, but when not specifying any acceleration, no fault occurred.

Let me know if you need me to develop a minimum example to debug from. At the moment it's all part of a slightly more complicated bit of code.

Version: 5.2.0 (compiled from source)
Command line options: -smp cores=4 -m 8192 (plus whatever uefi-run adds to plug in OVMF and my UEFI application).
Environment: Ubuntu 20.04 on Ryzen 3700X