diff --git a/.github/workflows/pre-commit.yml b/.github/workflows/pre-commit.yml
index 3a45a8d..ea8395a 100644
--- a/.github/workflows/pre-commit.yml
+++ b/.github/workflows/pre-commit.yml
@@ -3,6 +3,7 @@ name: pre-commit
   push:
     branches:
       - main
+      - dev
   pull_request:
     branches:
       - main
diff --git a/.pylintrc b/.pylintrc
index c750be3..eeb1929 100644
--- a/.pylintrc
+++ b/.pylintrc
@@ -16,8 +16,8 @@ max-args = 6
 disable =
   abstract-method,
   arguments-differ,
+  assigning-non-slot,  # pylint does not understand descriptors like WeakAttr in _orderedbase.py
   attribute-defined-outside-init,
-  class-variable-slots-conflict,  # pylint does not understand descriptors like WeakAttr in _orderedbase.py
   invalid-name,
   line-too-long,
   missing-function-docstring,  # flags @typing.overload's
diff --git a/bidict/_base.py b/bidict/_base.py
index 7458a6e..9c24111 100644
--- a/bidict/_base.py
+++ b/bidict/_base.py
@@ -47,12 +47,6 @@ dict_keys: t.Type[t.KeysView[t.Any]] = type({}.keys())
 BidictKeysView.register(dict_keys)
 
 
-# See _set_reversed() below.
-def _fwdm_reversed(self: t.Any) -> t.Iterator[KT]:
-    """Iterator over the contained keys in reverse order."""
-    return reversed(self._fwdm)
-
-
 def get_arg(*args: MapOrIterItems[KT, VT]) -> MapOrIterItems[KT, VT]:
     """Ensure there's only a single arg in *args*, then return it."""
     if len(args) > 1:
@@ -127,17 +121,17 @@ class BidictBase(BidirectionalMapping[KT, VT]):
         cls._inv_cls = cls._make_inv_cls()
 
     @classmethod
-    def _make_inv_cls(cls, _miss: t.Any = object()) -> 't.Type[BidictBase[VT, KT]]':
+    def _make_inv_cls(cls: t.Type[BT], _miss: t.Any = object()) -> 't.Type[BT]':
         diff = cls._inv_cls_dict_diff()
         cls_is_own_inv = all(getattr(cls, k, _miss) == v for (k, v) in diff.items())
         if cls_is_own_inv:
-            return t.cast(t.Type[BidictBase[VT, KT]], cls)
+            return cls
         # Suppress auto-calculation of _inv_cls's _inv_cls since we know it already.
         # Works with the guard in BidictBase._ensure_inv_cls() to prevent infinite recursion.
         diff['_inv_cls'] = cls
         inv_cls = type(f'{cls.__name__}Inv', (cls, GeneratedBidictInverse), diff)
         inv_cls.__module__ = cls.__module__
-        return inv_cls
+        return t.cast(t.Type[BT], inv_cls)
 
     @classmethod
     def _inv_cls_dict_diff(cls) -> t.Dict[str, t.Any]:
@@ -537,6 +531,13 @@ class BidictBase(BidirectionalMapping[KT, VT]):
         return self._from_other, (cls, dict(init_from), should_invert)  # type: ignore [call-overload] # https://github.com/python/mypy/issues/4975
 
 
+# See BidictBase._set_reversed() above.
+def _fwdm_reversed(self: BidictBase[KT, t.Any]) -> t.Iterator[KT]:
+    """Iterator over the contained keys in reverse order."""
+    assert isinstance(self._fwdm, t.Reversible)
+    return reversed(self._fwdm)
+
+
 BidictBase._init_class()
 
 
diff --git a/bidict/_dup.py b/bidict/_dup.py
index 51a7803..2ce937a 100644
--- a/bidict/_dup.py
+++ b/bidict/_dup.py
@@ -8,8 +8,8 @@
 """Provide :class:`OnDup` and related functionality."""
 
 
-from collections import namedtuple
 from enum import Enum
+import typing as t
 
 
 class OD(Enum):
@@ -31,7 +31,7 @@ DROP_OLD = OD.DROP_OLD
 DROP_NEW = OD.DROP_NEW
 
 
-class OnDup(namedtuple('_OnDup', 'key val kv')):
+class OnDup(t.NamedTuple('_OnDup', [('key', OD), ('val', OD), ('kv', OD)])):
     r"""A 3-tuple of :class:`OD`\s specifying how to handle the 3 kinds of duplication.
 
     *See also* :ref:`basic-usage:Values Must Be Unique`
@@ -42,7 +42,7 @@ class OnDup(namedtuple('_OnDup', 'key val kv')):
 
     __slots__ = ()
 
-    def __new__(cls, key: OD = DROP_OLD, val: OD = RAISE, kv: OD = RAISE) -> 'OnDup':
+    def __new__(cls, key: OD = DROP_OLD, val: OD = RAISE, kv: t.Optional[OD] = None) -> 'OnDup':
         """Override to provide user-friendly default values."""
         return super().__new__(cls, key, val, kv or val)
 
diff --git a/bidict/_orderedbase.py b/bidict/_orderedbase.py
index e33adca..1c273a5 100644
--- a/bidict/_orderedbase.py
+++ b/bidict/_orderedbase.py
@@ -56,8 +56,6 @@ class Node:
 
     prv: 'WeakAttr[Node, Node]' = WeakAttr(slot='_prv_weak')
     __slots__ = ('_prv_weak', 'nxt', '__weakref__')
-    if t.TYPE_CHECKING:  # no 'prv' in __slots__ makes mypy think we don't have a 'prv' attr, so trick it:
-        __slots__ = ('prv', 'nxt', '__weakref__')
 
     def __init__(self, prv: 'Node', nxt: 'Node') -> None:
         self.prv = prv