Conflict With WooCommerce Coupon

I love this plugin. It works so fluently.

I do have one problem.

When I add a coupon code using WooCommerce, it does not apply the correct discount. This is because the Woocommerce coupon discounts of the product price, not the bulk price.

How can I fix this?

Example:

If product quantity is 1 the unit price is $5
– When I add 50% off coupon the new price is $2.50 (good)

If the product quantity is 100 the unit price is $1
– When I add 50% off coupon the new price is $250 (bad. It should be $50)