The cell envelope of Gram-negative bacteria, which is composed of the inner membrane, the peptidoglycan cell wall and the outer membrane, enables cells to withstand mechanical loads. It was previously thought that the mechanical integrity of the cell envelope is conferred by the cell wall; however, Rojas et al. report that the outer membrane has load-bearing capacity. Genetic or chemical perturbations to the outer membrane increased deformation of the cell envelope in response to different types of load, suggesting that the mechanical properties of the envelope are dependent on the composition and integrity of the outer membrane. Compromising the outer membrane reduced cell survival during osmotic fluctuation and proliferation of L-form bacteria, which lack a cell wall. Thus, both the cell wall and the outer membrane contribute to the mechanical properties of the cell envelope.