The popular German digital startup Fidor Bank has agreed to be acquired by Groupe BPCE, the second-largest French bank.

Founded in 2009, Fidor is one of the first and most notable of the so-called challenger banks, digital-only banks that have mostly popped up in the U.K. and Germany. Among the investors selling their equity to Groupe BPCE include Anthemis Group, a London-based investment firm that specifically targets fintech startups. The deal is set to close in the fourth quarter. The price was not disclosed.

BPCE said in a press release the acquisition is part of the ongoing rollout of its new digital strategy. In addition to operating its own banking enterprise, Fidor has developed a proprietary digital banking platform — Fidor Operating System — that facilitates banking through application programming interfaces. Fidor Operating System will be offered as a white-label service through BPCE.

"This operation constitutes a key step in the acceleration of the digital transformation of our group," François Pérol, the chairman of Groupe BPCE, said in the press release. "It further demonstrates our commitment to innovation, to develop a customer centric approach enabled by a digital banking technology and to be more involved in digital and mobile banking field."