X, in a filing in Wilmington, Delaware federal court Monday, said six former employees who sued the company in May were not parties to a 2022 merger agreement between Twitter and a Musk-owned holding company, so they cannot sue them for allegedly breaching it.

Lawyers for Musk in a separate filing said claims against him should be tossed out because he did not sign a specific provision of the merger agreement involving employee benefits, including severance pay.

The plaintiffs, who were based out of New York, California and Texas and had held various senior roles at Twitter, say the company failed to pay them severance totaling more than $1 million after they lost their jobs last year.

Twitter laid off more than half its workforce as a cost-cutting measure after Musk acquired the company last October.

Lawyers for the plaintiffs did not immediately respond to requests for comment on Tuesday.

The lawsuit is not a class action, but two similar pending lawsuits brought on behalf of much larger groups of former Twitter employees claim the company owes more than $500 million in severance pay. X has said all of the workers were paid in full.

The company is also facing a series of other lawsuits stemming from the layoffs that began last year, including claims that it targeted women and workers with disabilities.

Twitter has denied wrongdoing in the cases in which it has filed responses.