diff -r c89febab4648 Lib/test/test_cellleak.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Lib/test/test_cellleak.py	Thu May 09 09:11:31 2013 -0700
@@ -0,0 +1,56 @@
+"""Tests for issue 17927.
+
+The issue was that if self was part of a cycle involving the frame of
+a method call, *and* the method contained a nested function
+referencing self, thereby forcing 'self' into a cell, setting self to
+None would not be enough to break the frame -- the frame had another
+reference to the instance, which could not be cleared by the code
+running in the frame (though it will be cleared when the frame is
+collected).  Without the lambda, setting self to None is enough to
+break the cycle.
+
+NOTE: This test is specific to CPython.  It depends on reference
+counting.
+"""
+
+import gc
+import test.support
+import unittest
+
+
+class CellLeakTest(unittest.TestCase):
+
+    def test_cell_leak(self):
+        logs = []
+        class Canary:
+            def __del__(self):
+                logs.append('canary')
+        class Base:
+            def dig(self):
+                pass
+        class Tester(Base):
+            def __init__(self):
+                self.canary = Canary()
+            def dig(self):
+                if 0:
+                    lambda: self
+                try:
+                    1/0
+                except Exception as exc:
+                    self.exc = exc
+                super().dig()
+                self = None  # Break the cycle
+        tester = Tester()
+        tester.dig()
+        del tester
+        logs.append('collect')
+        gc.collect()
+        self.assertEqual(logs, ['canary', 'collect'])
+
+
+def test_main():
+    test.support.run_unittest(CellLeakTest)
+
+
+if __name__ == "__main__":
+    test_main()
diff -r c89febab4648 Objects/typeobject.c
--- a/Objects/typeobject.c	Wed May 08 18:12:35 2013 +0200
+++ b/Objects/typeobject.c	Thu May 09 09:11:31 2013 -0700
@@ -6510,6 +6510,10 @@
             return -1;
         }
         obj = f->f_localsplus[0];
+        if (obj != NULL && PyCell_Check(obj)) {
+	  /* It might be a cell.  See cell var initialization in ceval.c. */
+            obj = PyCell_GET(obj);
+        }
         if (obj == NULL) {
             PyErr_SetString(PyExc_RuntimeError,
                             "super(): arg[0] deleted");
diff -r c89febab4648 Python/ceval.c
--- a/Python/ceval.c	Wed May 08 18:12:35 2013 +0200
+++ b/Python/ceval.c	Thu May 09 09:11:31 2013 -0700
@@ -3519,8 +3519,13 @@
         int arg;
         /* Possibly account for the cell variable being an argument. */
         if (co->co_cell2arg != NULL &&
-            (arg = co->co_cell2arg[i]) != CO_CELL_NOT_AN_ARG)
+            (arg = co->co_cell2arg[i]) != CO_CELL_NOT_AN_ARG) {
             c = PyCell_New(GETLOCAL(arg));
+	    /* Reference the cell from the argument slot, for super().
+	       See typeobject.c. */
+	    Py_INCREF(c);
+	    SETLOCAL(arg, c);
+	}
         else
             c = PyCell_New(NULL);
         if (c == NULL)