(Reuters) — A federal judge on Thursday denied approval of a proposed settlement in a class-action suit against ride-hailing company Lyft, saying the $12.25 million deal “shortchanged” drivers by potentially half the sum they deserve.

U.S. District Judge Vince Chhabria said in a San Francisco court filing that the sum “does not fall within the range of reasonableness” and asked attorneys to offer another deal no later than May.

The 2013 lawsuit brought against Lyft by California drivers contended they should be classified as employees and therefore entitled to reimbursement for expenses, including gas and vehicle maintenance.