How can I get rid of the 'WARNING: Installing to ~/.gem since ... and ... aren't both writable." warning?

I like that it installs into ~/.gem, I just wish it would stop warning me about it.

Setting a $GEM_HOME doesn't seem like a solution, since I use both gem18 and gem19 (I've got to support both), and I like that the gems for each install into ~/.gem/ruby/<version>, and when I set a $GEM_HOME gems for each get install开发者_如何学Pythoned in the same directory.

Have you considered RVM? Especially if you play with multiple ruby versions. For me the biggest bonus is project specific gemsets with automatic switching.