FX FX Crown MKII Safety O-Ring

I took the stock off my FX Crown MKII last night for the 1st time following the instructions in the “FX Crown MKII Full Disassembly - FX Masterclass” Youtube video. In the video, he shows an o-ring on the safety which is not on my rifle.

Should I have one and what type is it? I don’t see this o-ring on the FX diagram:

https://fxairguns.com/wp-content/uploads/2021/05/Crown.pdf

Thanks Much, Bill