  We study the dynamics of strings with non-zero winding number around
T-duality defects. We deduce that the physics near the core of such
non-geometric objects involves winding modes that are not captured by the
supergravity approximation, and we argue that such corrections are T-dual to
the modes responsible for quantum corrections of semi-flat elliptic metrics. We
furthermore construct a solution of double field theory that captures part of
such near-core physics.
