Wierd keydown script error

[mindstorm 8]

I have this line of code:

(finddisplay 46) displayAddEventHandler ["keydown", "_this call FNC_RESET;"];

It works, aka it excecutes the functions flawlesly. However I still get an error:

Error in expression <_this call FNC_RESET;>
 Error position: <_this call FNC_RESET;>
 Error Type Script, expected Bool

How is this possible?

[Larrow 2797]

What does FNC_RESET look like? Is the error because of

From displayAddEventHandler on the BIKI

The provided function should return true/false indicating that the event has handled this event fully or not and whether the engine should execute it's default code or not afterwards.

[mindstorm 8]

You just made my day.

thx