Question about "nameof"

Can anybody tell me what is wrong with the following code?

In other words, I try to grab the name of my basering into s, and want to switch to this ring later. How should I get this to work? Right now it tells me:

I strongly suspect this has worked for an old version of Singular (maybe 2.0).

It still works as before by writing

setring `s`;
> ring r=0,x,dp;
> string s = nameof(basering);
> // define another ring
> ring r2 = real,x,dp;
> basering;
// characteristic : 0 (real)
// number of vars : 1
// block 1 : ordering dp
// : names x
// block 2 : ordering C

> back to the previous ring
> setring `s`;
> basering;
// characteristic : 0
// number of vars : 1
// block 1 : ordering dp
// : names x
// block 2 : ordering C



Another possibility is to use:

def d = basering;

setring d;

Thanks a lot, that worked!