IF Function not working with subtraction

Not sure what I'm doing wrong here or if this is a glitch in Excel,

EX:

A1 = 50.50

A2 = 50.10

A3 = 0.40

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

FORMULA:

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

For some reason the function always returns "Not Zero" even though A4 equals to 0.

How do I fix this? Thanks in advance!