Hi, I am trying to implement some MITC elements in firedrake using an approach similar to the one used by the fenics-shells project, using SLATE and static condensation. This is the symbolic expression that I am trying to compile, M_1[(range(0, 2), range(0, 2))]_0 + M_1[(range(0, 2), 3)]_2 * (M_1[(2, 3)]_3).inv * M_1[(2, 2)]_4 * (M_1[(3, 2)]_5).inv * M_1[(3, range(0, 2))]_6 However when I tried to assemble the condensed matrix, I got the following error, NotImplementedError: Compiling mixed slate expression Is there a way to work around this? If I explicitly write out each of the blocks for example? Thanks! Subramanya. सुब्रह्मण्य .