Installing puppetlabs-nodejs module results in SSL certificate error

When I try to install the puppetlabs-nodejs module on Ubuntu 12.04 it returns an SSL error. Here's the command:

puppet module install puppetlabs-nodejs --version 0.2.1

The error:

Error: Could not connect via HTTPS to https://forge.puppetlabs.com
Unable to verify the SSL certificate The certificate may not be signed by a valid CA The CA bundle included with OpenSSL may not be valid or up to date

Any ideas on what may be causing this? Google searches didn't provide much helpful information.