Clathrin mediated endocytosis is an essential and complex cellular process involving more than 60 proteins. In yeast, successful endocytosis requires counteracting a large turgor pressure. To this end, yeasts assemble actin patches, which accumulate elastic energy during their assembly. We investigated the material properties of reconstituted actin patches from a wild-type (WT) strain and a mutant strain lacking the cross-linker Sac6 (sac6), which has reduced endocytosis efficiency in live cells. We hypothesized that a change in the viscous properties of the actin patches, which would dissipate more mechanical energy, could explain this reduced efficiency. There was however no significant difference in the viscosity of both types of patches. However, we discovered a significantly different non-linear elastic response. While WT patches had a constant elastic modulus at different stresses, sac6 patches had a lower elastic modulus at low stresses, before stiffening at higher ones, up to values similar to WT patches. To understand the consequences of this discovery, we performed, in-vivo, a precise analysis of actin patch dynamics. Our analysis reveals that a small fraction of actin patches successfully complete endocytosis in sac6 cells, provided that those assemble an excess of actin at the membrane compared to WT. This observation indicates that non-linear elastic properties of actin networks in sac6 cells contribute to rescue endocytosis, requiring nevertheless more actin material to build-up the necessary stored elastic energy.