Custom Format - Show Zeros

Hello,
I am using the custom format to add text to a number (but still have the number used in calculations).

Under Format Cells->Number->Custom, I have changed my format to '### "Units" '. Whenever a number calculates in the cell it returns "54 Units", etc...

There are times when the number is zero (0). When the number is zero, it does not return "0 Units". Rather it just says "Units".

How can redo the formatting so it will say "0 Units" when the calculation returns zero?

Any feedback helps. Thank you.