Problem with the "input:down" function

[jr-uk]

I'm running through the Love2d tutorial and the below code causes the below error

function love.update(dt)
if input:down('kp+', 0.25) then increment() end
end

"Error

libraries/boipushy/input.lua:166: bad argument #1 to 'ipairs' (table expected, got nil)

Traceback

[C]: in function 'ipairs'
libraries/boipushy/input.lua:166: in function 'down'
main.lua:51: in function main.lua:48
libraries/boipushy/input.lua:61: in function 'update'
[C]: in function 'xpcall'"

[jr-uk]

Resolved, my error. Needed to associate with an action not a key.