We report on laboratory friction experiments measuring the frictional behavior of the input sediments offshore northern Sumatra, sampled during IODP Expedition 362. We performed laboratory friction experiments on eight different samples from the targeted depth interval in a GIESA RS5 single-direct shear device at room temperature, in-situ effective normal stresses, and under saturation with simulated seawater. The results show that the North Sumatra subduction zone input sediments which have been correlated with the protodécollement horizon are frictionally unstable, and also frictionally weak. Our results provide an explanation for shallow earthquake slip at Sumatra.