Apply percentage fee based on the post-discount order amount, instead of the list prices

I have set up a promo/coupon using "Percentage off the order subtotal".

I have a fee set up that is using "Percentage of order subtotal added to the order total" (and I also tried with a fee using "Percentage of each matching product added to the order total", encountering the same issues I outline below).

When I am in the cart and I choose the relevant payment method, the fee is calculated and added correctly.

However, if I then add a discount in the cart, the fee is calculated against the product/cart's pre-discount amount, rather than the product/cart's post-discount amount.

For example, if I have a $100 product in my cart, the fee (5%) is $5. If I then apply a 50% off coupon, I would expect the fee to be reduced to $2.50, since the product total in my cart is now $50, and the fee is supposed to be based on the order's subtotal or the matching products.

Is there a configuration that will accomplish this? If not, what would need to be changed/patched in the code to allow this to work in this fashion?