Custom code linking problem

Add a new custom code node.
Add a new float input.
Duplicate this node, place them side by side.
Start dragging a link from the right node's output. Note how the input of the left node is ghosted in spite matching types.
Add a new value node.
Link it to the left node's input. Should work fine.

(Doing _something_ makes it snap back to work properly but I can't repro it.)