diff --git a/changelog/12424.bugfix.rst b/changelog/12424.bugfix.rst
new file mode 100644
index 000000000..7ad112685
--- /dev/null
+++ b/changelog/12424.bugfix.rst
@@ -0,0 +1 @@
+Fix crash with `assert testcase is not None` assertion failure when re-running unittest tests using plugins like pytest-rerunfailures. Regressed in 8.2.2.
diff --git a/src/_pytest/unittest.py b/src/_pytest/unittest.py
index 56a9c5d09..0f201d0f3 100644
--- a/src/_pytest/unittest.py
+++ b/src/_pytest/unittest.py
@@ -223,7 +223,7 @@ class TestCaseFunction(Function):
             self._explicit_tearDown()
             self._explicit_tearDown = None
         self._obj = None
-        self._instance = None
+        del self._instance
         super().teardown()
 
     def startTest(self, testcase: "unittest.TestCase") -> None:
diff --git a/testing/plugins_integration/pytest_rerunfailures_integration.py b/testing/plugins_integration/pytest_rerunfailures_integration.py
new file mode 100644
index 000000000..9a13a3279
--- /dev/null
+++ b/testing/plugins_integration/pytest_rerunfailures_integration.py
@@ -0,0 +1,11 @@
+import unittest
+
+
+class MyTestCase(unittest.TestCase):
+    first_time = True
+
+    def test_fail_the_first_time(self) -> None:
+        """Regression test for issue #12424."""
+        if self.first_time:
+            type(self).first_time = False
+            self.fail()
diff --git a/tox.ini b/tox.ini
index 0a3f0acf5..35b335a01 100644
--- a/tox.ini
+++ b/tox.ini
@@ -141,7 +141,7 @@ commands =
     pytest --cov=. simple_integration.py
     pytest --ds=django_settings simple_integration.py
     pytest --html=simple.html simple_integration.py
-    pytest --reruns 5 simple_integration.py
+    pytest --reruns 5 simple_integration.py pytest_rerunfailures_integration.py
     pytest pytest_anyio_integration.py
     pytest pytest_asyncio_integration.py
     pytest pytest_mock_integration.py