Prevent yarn from creating node_modules in monorepo root

I'm using yarn with monorepos that contain several packages. For examples packages foo and bar might be located in repo/foo and repo/bar within the monorepo root repo. The problem is that I sometimes accidentally run yarn without parameters in the repository root instead of the packages directories. This creates a repo/node_modules directory and a repo/yarn.lock file. Can I somehow prevent yarn from creating node_modules and yarn.lock in the repository root directory?