diff --git a/changelog.d/16953.misc b/changelog.d/16953.misc
new file mode 100644
index 00000000000..81abcc3df02
--- /dev/null
+++ b/changelog.d/16953.misc
@@ -0,0 +1 @@
+Specify IP subnets in canonical form.
diff --git a/tests/api/test_auth.py b/tests/api/test_auth.py
index ce85ddf22aa..bd229cf7e9c 100644
--- a/tests/api/test_auth.py
+++ b/tests/api/test_auth.py
@@ -128,7 +128,7 @@ def test_get_user_by_req_appservice_valid_token_good_ip(self) -> None:
             token="foobar",
             url="a_url",
             sender=self.test_user,
-            ip_range_whitelist=IPSet(["192.168/16"]),
+            ip_range_whitelist=IPSet(["192.168.0.0/16"]),
         )
         self.store.get_app_service_by_token = Mock(return_value=app_service)
         self.store.get_user_by_access_token = AsyncMock(return_value=None)
@@ -147,7 +147,7 @@ def test_get_user_by_req_appservice_valid_token_bad_ip(self) -> None:
             token="foobar",
             url="a_url",
             sender=self.test_user,
-            ip_range_whitelist=IPSet(["192.168/16"]),
+            ip_range_whitelist=IPSet(["192.168.0.0/16"]),
         )
         self.store.get_app_service_by_token = Mock(return_value=app_service)
         self.store.get_user_by_access_token = AsyncMock(return_value=None)