A prosthetic valve includes a tubular portion coupled to an upstream support portion, and ventricular legs. The prosthetic valve is transitionable from a compressed state into a partially-expanded state in which (1) a downstream surface of the support portion defines (i) an annular concave region extending radially between a concave-region inner radius and a concave-region outer radius, and (ii) an annular convex region, radially outward from the annular concave region, extending radially between a convex-region inner radius and a convex-region outer radius, and (2) the tip of each leg is disposed radially between the concave-region inner radius and the concave-region outer radius. In a fully-expanded state each leg's tip is disposed radially between the convex-region inner radius and the convex-region outer radius. Other embodiments are also described.