Unknown keypress

The key you just pressed is not recognized by SDL. To help get this fixed, please report this to the SDL forums/mailing list <https://discourse.libsdl.org/> X11 KeyCode 248 (240), X11 KeySym 0x0 ((null)).The key you just pressed is not recognized by SDL. To help get this fixed, please report this to the SDL forums/mailing list <https://discourse.libsdl.org/> X11 KeyCode 248 (240), X11 KeySym 0x0 ((null)).

Got this error while running my game.