Development Finance Institutions (DFIs) exist to promote development by investing in the poorest, least developed countries. They often route those investments via holding companies or private equity funds domiciled in tax havens. On the face of it, that seems absurd: tax havens are widely seen as a drain on development, depriving cash-strapped governments of billions of dollars in public revenue. In a new paper I argue that whilst widespread opposition to DFIs investing via tax havens is understandable, it is misguided. Banning the use of tax havens would do more harm than good.