Notice error shown in WooCommerce e-mails

Hi,

Unfortunately our customers see a ‘not so nice’ notice error in the email after their order is received/processed/completed.

The following error is shown under the ‘price’ section after activating the discount plugin (check screenshot):

Notice: get_product is verouderd sinds versie 3.0. Gebruik in plaats daarvan wc_get_product. in /home/u47983p44249/domains/goedebuursilentdisco.nl/public_html/wp-includes/functions.php on line 4440
€249 (excl. btw)

Disabling the plugin solves the problem. However, I’d like to keep using this nice plugin! Any chance this can be fixed?

The page I need help with: [log in to see the link]