Fatal error: you must specify '--save', '--no-save' or '--vanilla'

Hi, I get the above error when starting my program with rake (ruby make) 
instead of manual startup (which works as expected).
It happens on R initialization with "REmbeddedPostgres --gui=none 
--silent" as arguments (this is part of my way of embedding R in a C 
application using libR.so). Any help would be appreciated!

Greetings,
Andreas