Problems with the constellation decoder block

[Thomas Lorblanchès]

Hi all,

I have some problems using the constellation receiver block (GnuRadio 3.7.13.4 
on Debian 10).
I have the following very simple flowgraph:
Constant source (value: 1-1j), a throttle block, a constellation decoder, a 
"char to float" block and then a QT GUI Time Sink block.
The constellation object used by the constellation decoder is configured with:
* Constellation type: Variable constellation
* Symbol map: [0,1,3,2]
* Constellation points: [-1-j,-1+1j,1+1j,1-1j]
* Rotational Symmetry: 4
* Dimensionality: 1

With such configuration, I would expect that the output of the constellation 
decoder is 2 (because constellation point 1-1j is mapped to the value 2). 
However, it is 3!?! I can change the "symbol map" all the way I want, the 
output is always 3, even with symbol map = [4,5,6,7].
Is there something I don't understand about how the constellation decoder block 
works?

Thanks for your help.
Regards,
Thomas