In a true David vs Goliath battle, the largest fast-food chain in the world has lost the EU trademark rights to its signature dish, following a challenge by a relatively unknown Irish rival.

Regulators at the European Union’s Intellectual Property Office (EUIPO) on Friday found that McDonald’s had failed to prove “genuine use” of the ‘Big Mac’ trademark across the EU over the last five years.

In comes in response to a challenge issued by small Irish chain, Supermac’s, which had previously been prohibited from expanding into the U.K. and Europe in fear of breaching trademark laws due to the similarity of the two names.

Speaking with Reuters, Pat McDonagh, Supermac’s founder said the decision was an unexpected delight.

“Supermac’s are delighted with their victory in the trademark application and in revoking the ‘Big Mac’ trademark which had been in existence since 1996,” McDonagh told Reuters.

“This is a great victory for business in general and stops bigger companies from ‘trademark bullying’ by not allowing them to hoard trademarks without using them.”

The judgement revokes McDonald’s registration of the trademark, allowing other companies as well as McDonald’s to use the ‘Big Mac’ name in the EU.

The iconic fast-food chain looks set to appeal the decision however, with CNBC reporting that the brand is confident the decision will be overturned.

“We are disappointed in the EUIPO’s decision and believe this decision did not take into account the substantial evidence submitted by McDonald’s proving use of our BIG MAC mark throughout Europe,” McDonald’s told CNBC in an email.

“We intend to appeal the decision and are confident it will be overturned by the EUIPO Board of Appeals.”

While the decision has no wider impact on McDonald’s Australian operation, the chain faced a similar challenge in November, when rival, Burger Urge launched its “Big Pac” burger.

The chain was forced to pull the Alpaca burger following a cease and desist notice issued by McDonald’s Australia which claimed the product infringed on the iconic ‘Big Mac’ trademark.