Group node interface: How to remove sockets?

Blender 2.71:
If I edit a group node in the node editor, i have a section named “Interface” in the right panel.

I can add input and output sockets by clicking on the “+” item below the list.
I can rearrange them with the up/down arrows on the left hand side.
But how can I delete one?
If I select one and type “x” or “Del”, nothing happens.

Thanks

Select a input or output from the interface lists and press X button next to the label line


Thanks.

Solving Blender mysteries on at the time :slight_smile: