rbenv: version is not installed

[yuvilio]

Got this error using rake with rbenv on linux :

$ ruby --version
ruby 2.1.5p273 (2014-11-13 revision 48405) [x86_64-linux]
$ rake
rbenv: version `2.0.0-p247' is not installed

Removing the .ruby-version file fixes it :

$ rm .ruby-version 
$ rake
mkdir -p build/dev/tmp
xxd -i src/style.css | sed 's/src_//g' > build/dev/tmp/style.css.h
gcc -I. -Ibuild/dev/tmp -Wall -g -c src/mdr.c -o build/dev/tmp/mdr.o
...
lgobject-2.0 -ljavascriptcoregtk-3.0 -lglib-2.0  -Ibuild/dev/tmp -o build/dev/mdr
$ 
$ ls build/dev/mdr 
build/dev/mdr
$ 

Should the README just point that out? Or is there something to fix here?

System tested on:

$ rbenv --version
rbenv 0.4.0-129-g7e0e85b
$ 
$ uname -a
Linux kamitsukai 3.16.0-29-generic #39-Ubuntu SMP Mon Dec 15 22:27:29 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
$