I installed "mean-cli" globally and all the packages are up-to-date. Also, I successfully installed "mean.io"; however, when I want to add additional modules with "mean" command, I get an error message.

When I type mean install upload or mean list, I get the following error message:

module.js:442
throw err;
^
Error: Cannot find module 'npm'

But the "mean" command does work with mean --help or mean register.