diff --git a/confirmation/models.py b/confirmation/models.py
index 262d196fee..6df9203e45 100644
--- a/confirmation/models.py
+++ b/confirmation/models.py
@@ -20,7 +20,7 @@ from django.utils.timezone import now as timezone_now
 from typing_extensions import override
 
 from confirmation import settings as confirmation_settings
-from zerver.lib.types import UnspecifiedValue
+from zerver.lib.types import UNSET, Unset
 from zerver.models import (
     EmailChangeStatus,
     MultiuseInvite,
@@ -129,7 +129,7 @@ def create_confirmation_object(
     obj: ConfirmationObjT,
     confirmation_type: int,
     *,
-    validity_in_minutes: int | None | UnspecifiedValue = UnspecifiedValue(),
+    validity_in_minutes: int | None | Unset = UNSET,
     no_associated_realm_object: bool = False,
 ) -> "Confirmation":
     # validity_in_minutes is an override for the default values which are
@@ -149,7 +149,7 @@ def create_confirmation_object(
 
     current_time = timezone_now()
     expiry_date = None
-    if not isinstance(validity_in_minutes, UnspecifiedValue):
+    if not isinstance(validity_in_minutes, Unset):
         if validity_in_minutes is None:
             expiry_date = None
         else:
@@ -172,7 +172,7 @@ def create_confirmation_link(
     obj: ConfirmationObjT,
     confirmation_type: int,
     *,
-    validity_in_minutes: int | None | UnspecifiedValue = UnspecifiedValue(),
+    validity_in_minutes: int | None | Unset = UNSET,
     url_args: Mapping[str, str] = {},
     no_associated_realm_object: bool = False,
 ) -> str:
diff --git a/pyproject.toml b/pyproject.toml
index 3bd365fad2..73a721d0ba 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -145,7 +145,6 @@ ignore = [
     "ANN102", # Missing type annotation for `cls` in classmethod
     "ANN401", # Dynamically typed expressions (typing.Any) are disallowed
     "B007", # Loop control variable not used within the loop body
-    "B008", # Do not perform function calls in argument defaults
     "B904", # Within an except clause, raise exceptions with raise ... from err or raise ... from None to distinguish them from errors in exception handling
     "C408", # Unnecessary `dict` call (rewrite as a literal)
     "COM812", # Trailing comma missing
diff --git a/zerver/lib/events.py b/zerver/lib/events.py
index 704243d9fd..d426418ec6 100644
--- a/zerver/lib/events.py
+++ b/zerver/lib/events.py
@@ -1746,6 +1746,9 @@ class ClientCapabilities(TypedDict):
     archived_channels: NotRequired[bool]
 
 
+DEFAULT_CLIENT_CAPABILITIES = ClientCapabilities(notification_settings_null=False)
+
+
 def do_events_register(
     user_profile: UserProfile | None,
     realm: Realm,
@@ -1760,7 +1763,7 @@ def do_events_register(
     all_public_streams: bool = False,
     include_subscribers: bool = True,
     include_streams: bool = True,
-    client_capabilities: ClientCapabilities = ClientCapabilities(notification_settings_null=False),
+    client_capabilities: ClientCapabilities = DEFAULT_CLIENT_CAPABILITIES,
     narrow: Collection[NarrowTerm] = [],
     fetch_event_types: Collection[str] | None = None,
     spectator_requested_language: str | None = None,
diff --git a/zerver/lib/types.py b/zerver/lib/types.py
index f6af9f30fc..b9cc54df94 100644
--- a/zerver/lib/types.py
+++ b/zerver/lib/types.py
@@ -69,7 +69,7 @@ class LinkifierDict(TypedDict):
     id: int
 
 
-class UnspecifiedValue:
+class Unset:
     """In most API endpoints, we use a default value of `None"` to encode
     parameters that the client did not pass, which is nicely Pythonic.
 
@@ -84,6 +84,9 @@ class UnspecifiedValue:
     """
 
 
+UNSET = Unset()
+
+
 class EditHistoryEvent(TypedDict, total=False):
     """
     Database format for edit history events.
diff --git a/zerver/tests/test_typed_endpoint.py b/zerver/tests/test_typed_endpoint.py
index 4a378616b9..f179850713 100644
--- a/zerver/tests/test_typed_endpoint.py
+++ b/zerver/tests/test_typed_endpoint.py
@@ -73,6 +73,8 @@ class TestEndpoint(ZulipTestCase):
 
             __pydantic_config__ = ConfigDict(extra="forbid")
 
+        default_foo = Foo(10, 10)
+
         @typed_endpoint
         def view(
             request: HttpRequest,
@@ -81,7 +83,7 @@ class TestEndpoint(ZulipTestCase):
             json_str: Json[str],
             json_data: Json[Foo],
             json_optional: Json[int | None] | None = None,
-            json_default: Json[Foo] = Foo(10, 10),
+            json_default: Json[Foo] = default_foo,
             non_json: str = "ok",
             non_json_optional: str | None = None,
         ) -> HttpResponse:
diff --git a/zerver/views/events_register.py b/zerver/views/events_register.py
index 0d48abc20e..63ae7068d8 100644
--- a/zerver/views/events_register.py
+++ b/zerver/views/events_register.py
@@ -9,7 +9,7 @@ from pydantic import Json
 
 from zerver.context_processors import get_valid_realm_from_request
 from zerver.lib.compatibility import is_pronouns_field_type_supported
-from zerver.lib.events import ClientCapabilities, do_events_register
+from zerver.lib.events import DEFAULT_CLIENT_CAPABILITIES, ClientCapabilities, do_events_register
 from zerver.lib.exceptions import JsonableError, MissingAuthenticationError
 from zerver.lib.narrow_helpers import narrow_dataclasses_from_tuples
 from zerver.lib.request import RequestNotes
@@ -46,7 +46,7 @@ def events_register_backend(
     presence_history_limit_days: Json[int] | None = None,
     all_public_streams: Json[bool] | None = None,
     include_subscribers: Json[bool] = False,
-    client_capabilities: Json[ClientCapabilities] | None = None,
+    client_capabilities: Json[ClientCapabilities] = DEFAULT_CLIENT_CAPABILITIES,
     event_types: Json[list[str]] | None = None,
     fetch_event_types: Json[list[str]] | None = None,
     narrow: Json[NarrowT] | None = None,
@@ -99,9 +99,6 @@ def events_register_backend(
         all_public_streams = False
         include_streams = False
 
-    if client_capabilities is None:
-        client_capabilities = ClientCapabilities(notification_settings_null=False)
-
     client = RequestNotes.get_notes(request).client
     assert client is not None