IWG plc has filed a lawsuit against WeWork.

The Switzerland-based company says that WeWork’s new business line — HQ by WeWork — infringes on a 28-year-old trademark registered to HQ Network Systems, which IWG acquired in 2004.

IWG inked the deal through a subsidiary, Regus Management.

The lawsuit, filed in Dallas federal court on Sept. 19, claims the HQ by WeWork brand could “cause confusion and deception in the marketplace” because IWG still has a brand called HQ Global Workplaces (h/t Bisnow).

It also alleges that WeWork unlawfully interfered with their businesses by offering brokers a 100 percent commission for leases with companies that occupied space with a competitor.

IWG’s HQ brand has existed since the 1970s, the company states. IWG operates in about 3,000 locations in 100 countries. Although it is best known for its Regus brand, it also operates flexible shared offices under the Spaces name, a WeWork rival that has been busy with a major expansion effort in North America.

WeWork, meanwhile, is backed by SoftBank and valued at more than $20 billion. The New York-based company has expanded aggressively around the world over the past few years. In New York, it recently surpassed JPMorgan Chase & Co. as the city’s largest corporate occupier.

The company filed a countersuit Oct. 9, denying all of IWG’s claims. It also issued a prepared statement in response to the lawsuit:

Headquarters, or its abbreviation HQ, is a a type of office space. We believe it should be available to all companies who offer headquarters or office space services.

IWG, through Regus, has asked the court to issue an injunction to prevent WeWork from using the “HQ by WeWork” brand. It is also seeking monetary damages and attorneys’ fees, the report continued.

This isn’t the only legal battle for WeWork in recent days. A former WeWork employee alleges that she was sexually assaulted at company events. She also claims that WeWork brass failed to intervene or hold her assailants accountable, citing an “entitled, frat-boy culture that permeates [it] from the top down.”

Ruby Anaya, 33, lives in New York City. She started working in WeWork’s technology department as a director of product management in 2014, according to NBC News. The lawsuit was filed against the company and its co-founder Miguel McKelvey in Manhattan Supreme Court on Thursday, Oct. 11.