Regression: redirect to another protocol then http: does not work anymore

In Grails 1.3 the following worked in a Grails controller:

def proto =

In Grails 2.0-RC3 the same fails because the generated URL is prefixed with the controllers URL, so the result is:
http://localhost:8080/GuiLinkabasurl:doesomething
Using parameters 'absolute' or 'base' does not change this behaviour.

However, when the protocol is followed by '//' the redirect URL is constructed correctly:

def proto =

results in
abasurl://dosomething

In my understanding redirect always should accept the given URL regardless of the prefix being 'abasurl:' or 'abasurl://'