The East Antarctic Ice Sheet (EAIS) is the largest reservoir of ice on the planet by an order of magnitude. Compared with the West Antarctic Ice Sheet (WAIS), it is traditionally considered to be relatively stable, with only minor adjustments to its configuration over glacial-interglacial cycles. Here, we present the results of a radio-echo sounding survey from Coats Land, East Antarctica, which suggests that parts of the EAIS outlet drainage system may have changed significantly since the Last Glacial Maximum. We have identified an enhanced flow unit from buckled internal layering and smooth bed morphology that is no longer active. We believe this feature to have shut down at some point since the Last Glacial Maximum, ∼20 ka BP.