diff --git a/src/libsemigroups_pybind11/detail/cxx_wrapper.py b/src/libsemigroups_pybind11/detail/cxx_wrapper.py
index e9d590900..1450f77cb 100644
--- a/src/libsemigroups_pybind11/detail/cxx_wrapper.py
+++ b/src/libsemigroups_pybind11/detail/cxx_wrapper.py
@@ -13,8 +13,9 @@
 """
 
 from functools import update_wrapper
-
+from inspect import isclass
 from types import MethodType
+
 from typing import Any, Callable
 from typing_extensions import Self
 
@@ -240,8 +241,13 @@ def copy_cxx_mem_fns(cxx_class: pybind11_type, py_class: CxxWrapper) -> None:
         if (not py_meth_name.startswith("_")) and py_meth_name not in dir(
             py_class
         ):
-            setattr(
-                py_class,
-                py_meth_name,
-                wrap_cxx_mem_fn(getattr(cxx_class, py_meth_name)),
-            )
+            if not isclass(getattr(cxx_class, py_meth_name)):
+                setattr(
+                    py_class,
+                    py_meth_name,
+                    wrap_cxx_mem_fn(getattr(cxx_class, py_meth_name)),
+                )
+            else:
+                setattr(
+                    py_class, py_meth_name, getattr(cxx_class, py_meth_name)
+                )
diff --git a/tests/test_knuth_bendix.py b/tests/test_knuth_bendix.py
index bf0a15e98..7f6a1aa38 100644
--- a/tests/test_knuth_bendix.py
+++ b/tests/test_knuth_bendix.py
@@ -15,6 +15,8 @@
 from datetime import timedelta
 import pytest
 
+from _libsemigroups_pybind11 import Runner  # pylint: disable=no-name-in-module
+
 from libsemigroups_pybind11 import (
     KnuthBendix,
     LIMIT_MAX,
@@ -29,6 +31,7 @@
     presentation,
 )
 
+
 from .runner import check_runner
 from .cong_common import check_congruence_common_return_policy
 
@@ -393,6 +396,12 @@ def test_knuth_bendix_return_policy():
     assert kb.gilman_graph_node_labels() is not kb.gilman_graph_node_labels()
 
 
+def test_knuth_bendix_runner_state():
+    p = Presentation([0, 1])
+    kb = KnuthBendix(congruence_kind.twosided, p)
+    assert isinstance(kb.state(0), Runner.state)
+
+
 # TODO(0) Does the alphabet bug persist? YES: the test fails
 # def test_alphabet_bug():
 #     p = Presentation("".join(chr(i) for i in range(-126, 128)))