protected function validate_coupon_sale_items( $coupon ) {
		if ( $coupon->get_exclude_sale_items() ) {
			$valid = true;

			foreach ( $this->get_items_to_validate() as $item ) {
				if ( $item->product && $item->product->is_on_sale() ) {
					$valid = false;
					break;
				}
			}

			if ( ! $valid ) {
				throw new Exception( __( 'Sorry, this coupon is not valid for sale items.', 'woocommerce' ), 110 );
			}
		}

		return true;
	}