Hi Andy, Thanks for the update! I spent some time checking whether dependents, as returned by ‘guix refresh -l vtk’, would still build. It turns out tha ‘mia’ no longer builds after this update because the ‘VTK_INCLUDE_DIRS’ CMake variable remains empty. I’m not familiar (or averse to?) CMake, and I couldn’t figure out why that is the case. Could you take a look? As a last resort, we could preserve VTK 8.2 and use it in MIA. Attached is my variant of the patch, which propagates libogg, as was needed for some dependents, but really we could/should propagate libtheora, lz4, and double-conversion for the same reasons it seems. Let me know what you think! Thanks, Ludo’.