wayneeseguin/rvm — comment on commit 26e27209bf3f2e2261c87561d7f64ef4afc18d31
File:  line 0
By mpapis:

have you tried:

rvm get head && rvm reload
rvm reinstall jruby --19

you need to `reload` only if your rvm is older then 1.10.0
the --19 switch will enable 1.9 mode by default in jruby (and rbx)