`sources` in .gemrc file appears to not be working

I cloned a repo with a very simple Gemfile:

# Gemfilegem "rspec"

Running bundle install threw this error:

$ bundle installYour Gemfile has no gem server sources. If you need gems that are not already on yourmachine, add a line like this to your Gemfile:source 'https://rubygems.org'Could not find rspec-support-3.2.2 in any of the sources

Not wanting to modify the Gemfile, I created ~/.gemrc like so:

# ~/.gemrcsources:- http://rubygems.org

Then, I closed and reopened the shell window.

The error did not change. The error resolved when I added source "http://rubygems.org" to the Gemfile.

Why didn't updating the .gemrc file resolve the error?