Basic IF Function Not working

Hi,

I cannot figure out why this basic IF function isn't working - is it a glitch or is there something I am missing?

EX:

A1 = 50.87

A2 = 50.32

A3 = 0.55

A4 = ((A1)-(A2)-(A3))

FUNCTION:

IF(A4=0,"Equal to Zero", "Not Equal")

This function always returns "Not Equal" - any reason why/what am I doing wrong?

Thanks in advance!