diff --git a/bidict/_base.py b/bidict/_base.py
index c7f42f6..a9140cc 100644
--- a/bidict/_base.py
+++ b/bidict/_base.py
@@ -410,10 +410,12 @@ class BidictBase(BidirectionalMapping[KT, VT]):
             ] if save_unwrite else []
         return write, unwrite
 
+    __NO_KW: t.Mapping[str, t.Any] = MappingProxyType({})
+
     def _update(
         self,
         arg: MapOrIterItems[KT, VT],
-        kw: t.Mapping[str, VT] = MappingProxyType({}),
+        kw: t.Mapping[str, VT] = __NO_KW,
         *,
         rbof: t.Optional[bool] = None,
         on_dup: t.Optional[OnDup] = None,
diff --git a/requirements/lint.txt b/requirements/lint.txt
index 992646b..d0b68d1 100644
--- a/requirements/lint.txt
+++ b/requirements/lint.txt
@@ -51,7 +51,7 @@ pylint==2.14.0
     # via -r requirements/lint.in
 pyparsing==3.0.9
     # via packaging
-pyright==1.1.246
+pyright==1.1.251
     # via -r requirements/lint.in
 pytest==7.1.2
     # via -r requirements/lint.in