Consider the following testcase

class X:
    def meth(self):
        print(self)
        super()

def f():
    k = X()
    def g():
        return k
    return g
c = f().__closure__[0]
X.meth(c)

With patch
$ ./python unboxing.py 
<cell at 0x7fddacab1eb8: X object at 0x7fddac7876d8>

Without patch
$ ./python unboxing.py
<cell at 0x7f2d0a218eb8: X object at 0x7f2d09eee6d8>
Traceback (most recent call last):
  File "x.py", line 12, in <module>
    X.meth(c)
  File "x.py", line 4, in meth
    super()
TypeError: super(type, obj): obj must be an instance or subtype of type

Maybe you don't care. OTOH, perhaps it could be fixed by checking if the first argument is in fact a closure in super().

In the best world, super() would be syntax instead of a call, and we would just push the __class__ the closure and first argument in the interpreter loop.