iMac IR sensor suddenly works, cannot de-activate

On my iMac (late 2009), I used to have the infrared sensor disabled. I don't use it, don't want to use it. I disabled the sensor through preferences, Security & Privacy, advanced, "Disable remote control infrared receiver". On Sierra, this worked fine!

Now after the installation of High Sierra, the option is still on, but unfortunately the iMac returned to respond to the IR remote. I tried to uncheck/check the option, but this doesn't work. Any idea's how to fix this?