Laravel validation of one field being greater than or equal to another field not working

I'm using Laravel 5.8.26 and am trying to validate that one field is greater than or equal to another field.

Here's my code:

'amountMin' => 'required|numeric|gte:0',
'amountMax' => 'required|numeric|gte:amountMin',

the value for amountMin is 5000 and the value for amountMax is 40000.

when my code runs I get the message that amountMax must be greater than or equal to amountMin.

I found this StackOverflow post that says in order to do this you have to create a custom validation rule, but according to the way I understand Laravel validators to work my code should work. Am I wrong, do I need to create a custom validation rule to ensure amountMax is greater than or equal to amountMin or do I just need to adjust my code a bit to get it to work?

As always a correct, clearly explained answer will be marked as accepted answer and upvoted.

Thanks in advance.

via Chebli Mohamed