Ah, then I bet I did one more thing: I likely renamed configure to configure.bak (or something similar), ran roxygen on it, then added configure back again. I don’t recall ever manually adding a line to the NAMESPACE file. Basically, I wanted to build the package without the dynamic lib, just to generate a namespace file that includes the useDynLib line. Then build it again with the rstan files available. After that, it should continue working fine.