diff --git a/Include/internal/pycore_pyerrors.h b/Include/internal/pycore_pyerrors.h
index 0f4d41c7e0bab8..14ea182f4f47aa 100644
--- a/Include/internal/pycore_pyerrors.h
+++ b/Include/internal/pycore_pyerrors.h
@@ -28,6 +28,8 @@ static inline void _PyErr_ClearExcState(_PyErr_StackItem *exc_state)
     Py_XDECREF(tb);
 }
 
+PyAPI_FUNC(PyObject*) _PyErr_StackItemToExcInfoTuple(
+    _PyErr_StackItem *err_info);
 
 PyAPI_FUNC(void) _PyErr_Fetch(
     PyThreadState *tstate,
diff --git a/Python/ceval.c b/Python/ceval.c
index 1d69708576fa47..0a775de075026c 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1101,7 +1101,7 @@ static void
 _assert_exception_type_is_redundant(PyObject* type, PyObject* val)
 {
     if (type == NULL || type == Py_None) {
-        assert(val == NULL || val == Py_None);
+        assert(val == type);
     }
     else {
         assert(PyExceptionInstance_Check(val));
@@ -3717,7 +3717,9 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, InterpreterFrame *frame, int thr
 
         TARGET(JUMP_IF_NOT_EXC_MATCH) {
             PyObject *right = POP();
-            PyObject *left = TOP();
+            ASSERT_EXC_TYPE_IS_REDUNDANT(TOP(), SECOND());
+            PyObject *left = SECOND();
+            assert(PyExceptionInstance_Check(left));
             if (check_except_type_valid(tstate, right) < 0) {
                  Py_DECREF(right);
                  goto error;
@@ -4177,7 +4179,13 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, InterpreterFrame *frame, int thr
             ASSERT_EXC_TYPE_IS_REDUNDANT(type, value);
             _PyErr_StackItem *exc_info = tstate->exc_info;
             SET_THIRD(exc_info->exc_traceback);
-            SET_SECOND(exc_info->exc_value);
+            if (exc_info->exc_value != NULL) {
+                SET_SECOND(exc_info->exc_value);
+            }
+            else {
+                Py_INCREF(Py_None);
+                SET_SECOND(Py_None);
+            }
             if (exc_info->exc_type != NULL) {
                 SET_TOP(exc_info->exc_type);
             }
@@ -5896,7 +5904,9 @@ do_raise(PyThreadState *tstate, PyObject *exc, PyObject *cause)
         type = exc_info->exc_type;
         value = exc_info->exc_value;
         tb = exc_info->exc_traceback;
-        if (Py_IsNone(type) || type == NULL) {
+        assert(((Py_IsNone(value) || value == NULL)) ==
+               ((Py_IsNone(type) || type == NULL)));
+        if (Py_IsNone(value) || value == NULL) {
             _PyErr_SetString(tstate, PyExc_RuntimeError,
                              "No active exception to reraise");
             return 0;
diff --git a/Python/errors.c b/Python/errors.c
index cb3938d20856fc..6e74d19b78ef33 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -79,11 +79,16 @@ _PyErr_StackItem *
 _PyErr_GetTopmostException(PyThreadState *tstate)
 {
     _PyErr_StackItem *exc_info = tstate->exc_info;
-    while ((exc_info->exc_type == NULL || exc_info->exc_type == Py_None) &&
+    assert(exc_info);
+
+    while ((exc_info->exc_value == NULL || exc_info->exc_value == Py_None) &&
            exc_info->previous_item != NULL)
     {
+        assert(exc_info->exc_type == NULL || exc_info->exc_type == Py_None);
         exc_info = exc_info->previous_item;
     }
+    assert(exc_info->previous_item == NULL ||
+           (exc_info->exc_type != NULL && exc_info->exc_type != Py_None));
     return exc_info;
 }
 
@@ -471,10 +476,20 @@ _PyErr_GetExcInfo(PyThreadState *tstate,
                   PyObject **p_type, PyObject **p_value, PyObject **p_traceback)
 {
     _PyErr_StackItem *exc_info = _PyErr_GetTopmostException(tstate);
-    *p_type = exc_info->exc_type;
+
     *p_value = exc_info->exc_value;
     *p_traceback = exc_info->exc_traceback;
 
+    if (*p_value == NULL || *p_value == Py_None) {
+        assert(exc_info->exc_type == NULL || exc_info->exc_type == Py_None);
+        *p_type = Py_None;
+    }
+    else {
+        assert(PyExceptionInstance_Check(*p_value));
+        assert(exc_info->exc_type == PyExceptionInstance_Class(*p_value));
+        *p_type = PyExceptionInstance_Class(*p_value);
+    }
+
     Py_XINCREF(*p_type);
     Py_XINCREF(*p_value);
     Py_XINCREF(*p_traceback);
@@ -507,42 +522,66 @@ PyErr_SetExcInfo(PyObject *p_type, PyObject *p_value, PyObject *p_traceback)
     Py_XDECREF(oldtraceback);
 }
 
+
+PyObject*
+_PyErr_StackItemToExcInfoTuple(_PyErr_StackItem *err_info)
+{
+    PyObject *exc_value = err_info->exc_value;
+    if (exc_value == NULL) {
+        exc_value = Py_None;
+    }
+
+    assert(exc_value == Py_None || PyExceptionInstance_Check(exc_value));
+
+    PyObject *exc_type = PyExceptionInstance_Check(exc_value) ?
+               PyExceptionInstance_Class(exc_value) :
+               Py_None;
+
+    return Py_BuildValue(
+        "(OOO)",
+        exc_type,
+        exc_value,
+        err_info->exc_traceback != NULL ?
+            err_info->exc_traceback : Py_None);
+}
+
+
 /* Like PyErr_Restore(), but if an exception is already set,
    set the context associated with it.
 
    The caller is responsible for ensuring that this call won't create
    any cycles in the exception context chain. */
 void
-_PyErr_ChainExceptions(PyObject *exc, PyObject *val, PyObject *tb)
+_PyErr_ChainExceptions(PyObject *typ, PyObject *val, PyObject *tb)
 {
-    if (exc == NULL)
+    if (typ == NULL)
         return;
 
     PyThreadState *tstate = _PyThreadState_GET();
 
-    if (!PyExceptionClass_Check(exc)) {
+    if (!PyExceptionClass_Check(typ)) {
         _PyErr_Format(tstate, PyExc_SystemError,
                       "_PyErr_ChainExceptions: "
                       "exception %R is not a BaseException subclass",
-                      exc);
+                      typ);
         return;
     }
 
     if (_PyErr_Occurred(tstate)) {
-        PyObject *exc2, *val2, *tb2;
-        _PyErr_Fetch(tstate, &exc2, &val2, &tb2);
-        _PyErr_NormalizeException(tstate, &exc, &val, &tb);
+        PyObject *typ2, *val2, *tb2;
+        _PyErr_Fetch(tstate, &typ2, &val2, &tb2);
+        _PyErr_NormalizeException(tstate, &typ, &val, &tb);
         if (tb != NULL) {
             PyException_SetTraceback(val, tb);
             Py_DECREF(tb);
         }
-        Py_DECREF(exc);
-        _PyErr_NormalizeException(tstate, &exc2, &val2, &tb2);
+        Py_DECREF(typ);
+        _PyErr_NormalizeException(tstate, &typ2, &val2, &tb2);
         PyException_SetContext(val2, val);
-        _PyErr_Restore(tstate, exc2, val2, tb2);
+        _PyErr_Restore(tstate, typ2, val2, tb2);
     }
     else {
-        _PyErr_Restore(tstate, exc, val, tb);
+        _PyErr_Restore(tstate, typ, val, tb);
     }
 }
 
@@ -567,7 +606,11 @@ _PyErr_ChainStackItem(_PyErr_StackItem *exc_info)
     } else {
         exc_info_given = 1;
     }
-    if (exc_info->exc_type == NULL || exc_info->exc_type == Py_None) {
+
+    assert( (exc_info->exc_type == NULL || exc_info->exc_type == Py_None) ==
+            (exc_info->exc_value == NULL || exc_info->exc_value == Py_None) );
+
+    if (exc_info->exc_value == NULL || exc_info->exc_value == Py_None) {
         return;
     }
 
@@ -579,21 +622,32 @@ _PyErr_ChainStackItem(_PyErr_StackItem *exc_info)
         tstate->exc_info = exc_info;
     }
 
-    PyObject *exc, *val, *tb;
-    _PyErr_Fetch(tstate, &exc, &val, &tb);
+    PyObject *typ, *val, *tb;
+    _PyErr_Fetch(tstate, &typ, &val, &tb);
 
-    PyObject *exc2, *val2, *tb2;
-    exc2 = exc_info->exc_type;
+    PyObject *typ2, *val2, *tb2;
+    typ2 = exc_info->exc_type;
     val2 = exc_info->exc_value;
     tb2 = exc_info->exc_traceback;
-    _PyErr_NormalizeException(tstate, &exc2, &val2, &tb2);
+#ifdef Py_DEBUG
+    PyObject *typ2_before = typ2;
+    PyObject *val2_before = val2;
+    PyObject *tb2_before = tb2;
+#endif
+    _PyErr_NormalizeException(tstate, &typ2, &val2, &tb2);
+#ifdef Py_DEBUG
+    /* exc_info should already be normalized */
+    assert(typ2 == typ2_before);
+    assert(val2 == val2_before);
+    assert(tb2 == tb2_before);
+#endif
     if (tb2 != NULL) {
         PyException_SetTraceback(val2, tb2);
     }
 
     /* _PyErr_SetObject sets the context from PyThreadState. */
-    _PyErr_SetObject(tstate, exc, val);
-    Py_DECREF(exc);  // since _PyErr_Occurred was true
+    _PyErr_SetObject(tstate, typ, val);
+    Py_DECREF(typ);  // since _PyErr_Occurred was true
     Py_XDECREF(val);
     Py_XDECREF(tb);
 
diff --git a/Python/pystate.c b/Python/pystate.c
index 273982b4bd2f56..c42dd88506bbe3 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -1341,11 +1341,7 @@ _PyThread_CurrentExceptions(void)
             if (id == NULL) {
                 goto fail;
             }
-            PyObject *exc_info = PyTuple_Pack(
-                3,
-                err_info->exc_type != NULL ? err_info->exc_type : Py_None,
-                err_info->exc_value != NULL ? err_info->exc_value : Py_None,
-                err_info->exc_traceback != NULL ? err_info->exc_traceback : Py_None);
+            PyObject *exc_info = _PyErr_StackItemToExcInfoTuple(err_info);
             if (exc_info == NULL) {
                 Py_DECREF(id);
                 goto fail;
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 3e2091e70ab8a6..13fae797b29c2c 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -785,12 +785,7 @@ sys_exc_info_impl(PyObject *module)
 /*[clinic end generated code: output=3afd0940cf3a4d30 input=b5c5bf077788a3e5]*/
 {
     _PyErr_StackItem *err_info = _PyErr_GetTopmostException(_PyThreadState_GET());
-    return Py_BuildValue(
-        "(OOO)",
-        err_info->exc_type != NULL ? err_info->exc_type : Py_None,
-        err_info->exc_value != NULL ? err_info->exc_value : Py_None,
-        err_info->exc_traceback != NULL ?
-            err_info->exc_traceback : Py_None);
+    return _PyErr_StackItemToExcInfoTuple(err_info);
 }