Input Manager - prevent keyboard keys mapping to Xbox controller buttons

Hi, I am working on the game which should be controlled with keyboard as well with a joystick. I am testing the game with my Xbox 360 controller and I defined one axis like this:

Now I am able to fill the FireBeam axis with space on keyboard and also with A button on my controller, but the problem is that space is also mapped on B controller button by default. The result is that I can fire with both A and B buttons, which is something I don´t really want (B button will have another functionality later).

Is there some easy way to prevent default keyboard-controller mapping, or should I figure out more advanced solution through scripting? Thanks for your answers!