Castlight Health Inc announced a restructuring program aimed at reducing its operating expenses by 10% to 15%.

The program comes about "due, in part, to the recent unexpected churn of a large customer," the company said in an earnings release. During the company's second-quarter earnings call, Castlight CEO John Doyle mentioned that one of its largest customers, Walmart Inc., decided not to migrate to Castlight Complete in 2019 and instead let its contract with Castlight expire at the end of 2018, according to the call transcript.

Actions associated with the restructuring program may be largely completed by Sept. 30 and the company expects to take a restructuring charge in the third quarter. The charge will be excluded from its full-year 2018 non-GAAP operating loss and non-GAAP net loss per share calculation.

Castlight expects its 2019 revenue performance to be negatively impacted by approximately $30 million due to Walmart's nonrenewal. In addition, the third-quarter 2018 restructuring efforts are expected to provide $15 million to $20 million in operating cost savings for the full year 2019.

Castlight also reiterated its 2018 financial outlook. The company continues to expect GAAP revenue of $150 million to $155 million, non-GAAP operating loss of $15 million to $20 million, and non-GAAP net loss per share of about 11 cents to 15 cents, based on approximately 137 million to 138 million shares.