protected function apply_coupon_custom( $coupon, $items_to_apply ) {
		$limit_usage_qty = 0;
		$applied_count   = 0;

		if ( null !== $coupon->get_limit_usage_to_x_items() ) {
			$limit_usage_qty = $coupon->get_limit_usage_to_x_items();
		}

		// Apply the coupon to each item.
		foreach ( $items_to_apply as $item ) {
			// Find out how much price is available to discount for the item.
			$discounted_price = $this->get_discounted_price_in_cents( $item );

			// Get the price we actually want to discount, based on settings.
			$price_to_discount = wc_remove_number_precision( ( 'yes' === get_option( 'woocommerce_calc_discounts_sequentially', 'no' ) ) ? $discounted_price : $item->price );

			// See how many and what price to apply to.
			$apply_quantity = $limit_usage_qty && ( $limit_usage_qty - $applied_count ) < $item->quantity ? $limit_usage_qty - $applied_count : $item->quantity;
			$apply_quantity = max( 0, apply_filters( 'woocommerce_coupon_get_apply_quantity', $apply_quantity, $item, $coupon, $this ) );

			// Run coupon calculations.
			$discount      = wc_add_number_precision( $coupon->get_discount_amount( $price_to_discount / $item->quantity, $item->object, true ) ) * $apply_quantity;
			$discount      = wc_round_discount( min( $discounted_price, $discount ), 0 );
			$applied_count = $applied_count + $apply_quantity;

			// Store code and discount amount per item.
			$this->discounts[ $coupon->get_code() ][ $item->key ] += $discount;
		}

		// Allow post-processing for custom coupon types (e.g. calculating discrepancy, etc).
		$this->discounts[ $coupon->get_code() ] = apply_filters( 'woocommerce_coupon_custom_discounts_array', $this->discounts[ $coupon->get_code() ], $coupon );

		return array_sum( $this->discounts[ $coupon->get_code() ] );
	}