how to run hashcat legacy rules on new hashcat v3?

(This is related to my other question.)

In an attempt to run rules that I previously had to run on CPU hashcat legacy, in hashcat v3, I try:

hashcat64.exe  --opencl-device-types 1

Which gets:

OpenCL Platform #1: NVIDIA Corporation
======================================
- Device #1: GeForce GTX 970, skipped

OpenCL Platform #2: Intel(R) Corporation
========================================
- Device #2: Intel(R) Core(TM) i3 CPU         550  @ 3.20GHz, 4061/16247 MB allocatable, 4MCU

But the rules get this warning:

WARNING: Cannot convert rule for use on OpenCL device in file  testCPU.rule on line 1741: @a

So how do I run a rule like "@a"?