diff --git a/pcapkit/foundation/registry/protocols.py b/pcapkit/foundation/registry/protocols.py
index 2c92d7f3f..459e2d03e 100644
--- a/pcapkit/foundation/registry/protocols.py
+++ b/pcapkit/foundation/registry/protocols.py
@@ -221,7 +221,7 @@ class rather than supplied by a caller, and this function is the funnel
     if not isinstance(protocol, type):
         raise RegistryError(f'protocol must be a class, not {protocol!r}')
     if not issubclass(protocol, ProtocolBase):
-        raise RegistryError(f'protocol must be a ProtocolBase subclass, not {protocol!r}')
+        raise RegistryError(f'protocol must be a Protocol subclass, not {protocol!r}')
 
     name = protocol.__name__.upper()
     incumbent = protocol_registry.get(name)
diff --git a/pcapkit/protocols/protocol.py b/pcapkit/protocols/protocol.py
index a96df0ec2..75b04a49f 100644
--- a/pcapkit/protocols/protocol.py
+++ b/pcapkit/protocols/protocol.py
@@ -1139,7 +1139,7 @@ def _next_layer_entry(cls, code: 'Any', protocol: 'ModuleDescriptor[ProtocolBase
         if not isinstance(protocol, type):
             raise RegistryError(f'protocol must be a class, not {protocol!r}')
         if not issubclass(protocol, ProtocolBase):
-            raise RegistryError(f'protocol must be a ProtocolBase subclass, not {protocol!r}')
+            raise RegistryError(f'protocol must be a Protocol subclass, not {protocol!r}')
         return protocol
 
     @classmethod
diff --git a/tests/foundation/reassembly/test_deferred_pickle_2423_unit.py b/tests/foundation/reassembly/test_deferred_pickle_2423_unit.py
index 7ab929a54..1463d3b7e 100644
--- a/tests/foundation/reassembly/test_deferred_pickle_2423_unit.py
+++ b/tests/foundation/reassembly/test_deferred_pickle_2423_unit.py
@@ -245,7 +245,7 @@ def test_setstate_still_accepts_the_first_revisions_flat_shape(self) -> None:
         """The flat ``{slot: value}`` shape the very first fix returned.
 
         Never released, but already pushed in an earlier revision of
-        :issue:`2424`'s fix -- accepting it costs nothing and protects anyone
+        :issue:`2423`'s fix -- accepting it costs nothing and protects anyone
         who pickled against that revision.
 
         """
diff --git a/tests/foundation/registry/test_protocols.py b/tests/foundation/registry/test_protocols.py
index 830a7db3c..c9132109a 100644
--- a/tests/foundation/registry/test_protocols.py
+++ b/tests/foundation/registry/test_protocols.py
@@ -438,7 +438,7 @@ def test_register_protocol_rejects_a_non_class_with_registry_error(self) -> None
             ('none', None, 'must be a class'),
             ('descriptor argument (not unwrapped here)',
              ModuleDescriptor('pcapkit.protocols.misc.raw', 'Raw'), 'must be a class'),
-            ('wrong class', object, 'ProtocolBase subclass'),
+            ('wrong class', object, 'Protocol subclass'),
         ):
             with self.subTest(value=label):
                 with self.assertRaises(RegistryError) as caught:
diff --git a/tests/protocols/test_register_class_guard_unit.py b/tests/protocols/test_register_class_guard_unit.py
index 853476a38..334fb469f 100644
--- a/tests/protocols/test_register_class_guard_unit.py
+++ b/tests/protocols/test_register_class_guard_unit.py
@@ -82,7 +82,7 @@ def test_wrong_class_still_raises_registry_error(self) -> None:
                 with mock.patch.dict(klass.__proto__):
                     with self.assertRaises(RegistryError) as caught:
                         klass.register(code, dict)  # type: ignore[arg-type]
-                self.assertIn('ProtocolBase subclass', str(caught.exception))
+                self.assertIn('Protocol subclass', str(caught.exception))
 
     def test_descriptor_naming_a_non_class_raises_registry_error(self) -> None:
         from pcapkit.corekit.module import ModuleDescriptor
@@ -107,7 +107,7 @@ def test_descriptor_naming_a_wrong_class_still_raises_registry_error(self) -> No
                 with mock.patch.dict(klass.__proto__):
                     with self.assertRaises(RegistryError) as caught:
                         klass.register(code, descriptor)  # type: ignore[arg-type]
-                self.assertIn('ProtocolBase subclass', str(caught.exception))
+                self.assertIn('Protocol subclass', str(caught.exception))
 
     def test_valid_class_and_descriptor_still_register(self) -> None:
         from pcapkit.corekit.module import ModuleDescriptor