Just to be complete here: This error is in fact caused by the old issue referenced by Dan. pacman2 writes incorrect md5sums into the DB when the file is listed in NoUpgrade. This is not an issue for those of us that have been running pacman3 for a while, as it would have rewritten the correct md5sums there on an upgrade. This was an oversight on my part, and I apologize to anyone this affected negatively. There are a few solutions to the issue, but I'd like to not introduce code changes to fix this. So I'll propose the following: 1) We know the packages this effects - it's a very small subset, unless someone added additional NoUpgrade entries. 2) A small shell script which sets the backup md5sums to all zeros for a given package could be written, with directions for users at the edge cases. 3) Run the script for all packages we know on post-install/post-upgrade from pacman. Any problems with this?