A fairly standard way around this is to make the package a Suggests: and to condition the use in code (or tests) via if (requireNamespace(pkageNameHere, quietly = TRUE) { .... } That method is described in Writing R Extensions too, and followed by a (very) large nunber of packages. Dirk -- https://dirk.eddelbuettel.com | @eddelbuettel | edd@debian.org