Dear Firedrakers, Since FEniCS have merged the UFL complex branch upstream, this branch is now obsolete and has been deleted from github. Users of the (experimental) complex branches should therefore switch to ufl master. From an existing Firedrake complex installation, type: cd src/ufl git checkout master The installation instructions for complex have been updated: https://github.com/firedrakeproject/firedrake/projects/4 Regards, David