For write-backs: no, since the interpreter will still write those values back into the destination cell For locals display: no, since nothing changes for the handling of fast locals For closure display: yes as, by default, debuggers will now print the closure cell, not the value the cell references - they'd need to be updated to display obj.cell_contents for items listed in co_freevars and co_cellvars. That's why PEP 588 needs to be a PEP - there's a language design question around the trade-off between requiring all future Python implementations to implement a new write-through proxy type solely for this use case, or instead requiring trace functions to cope with co_freevars and co_cellvars being passed through as cell objects, rather than as direct references to their values.