diff --git a/Include/cpython/abstract.h b/Include/cpython/abstract.h
index cba0f4c3130..5eb22ff61ec 100644
--- a/Include/cpython/abstract.h
+++ b/Include/cpython/abstract.h
@@ -147,18 +147,10 @@ PyAPI_FUNC(Py_ssize_t) PyObject_LengthHint(PyObject *o, Py_ssize_t);
 
 /* === Mapping protocol ================================================= */
 
-PyAPI_FUNC(int) _PyObject_RealIsInstance(PyObject *inst, PyObject *cls);
-
-PyAPI_FUNC(int) _PyObject_RealIsSubclass(PyObject *derived, PyObject *cls);
-
-/* For internal use by buffer API functions */
-PyAPI_FUNC(void) _Py_add_one_to_index_F(int nd, Py_ssize_t *index,
-                                        const Py_ssize_t *shape);
-PyAPI_FUNC(void) _Py_add_one_to_index_C(int nd, Py_ssize_t *index,
-                                        const Py_ssize_t *shape);
-
-/* Convert Python int to Py_ssize_t. Do nothing if the argument is None. */
+// Convert Python int to Py_ssize_t. Do nothing if the argument is None.
+// Cannot be moved to the internal C API: used by Argument Clinic.
 PyAPI_FUNC(int) _Py_convert_optional_to_ssize_t(PyObject *, void *);
 
-/* Same as PyNumber_Index but can return an instance of a subclass of int. */
+// Same as PyNumber_Index but can return an instance of a subclass of int.
+// Cannot be moved to the internal C API: used by Argument Clinic.
 PyAPI_FUNC(PyObject *) _PyNumber_Index(PyObject *o);
diff --git a/Include/internal/pycore_abstract.h b/Include/internal/pycore_abstract.h
index 9ba27487f5b..2733d8102e5 100644
--- a/Include/internal/pycore_abstract.h
+++ b/Include/internal/pycore_abstract.h
@@ -41,6 +41,13 @@ extern int _PyObject_HasLen(PyObject *o);
 extern Py_ssize_t _PySequence_IterSearch(PyObject *seq,
                                          PyObject *obj, int operation);
 
+/* === Mapping protocol ================================================= */
+
+extern int _PyObject_RealIsInstance(PyObject *inst, PyObject *cls);
+
+extern int _PyObject_RealIsSubclass(PyObject *derived, PyObject *cls);
+
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Objects/abstract.c b/Objects/abstract.c
index fecdb4e0723..80a40944d6d 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -517,7 +517,7 @@ PyBuffer_GetPointer(const Py_buffer *view, const Py_ssize_t *indices)
 }
 
 
-void
+static void
 _Py_add_one_to_index_F(int nd, Py_ssize_t *index, const Py_ssize_t *shape)
 {
     int k;
@@ -533,7 +533,7 @@ _Py_add_one_to_index_F(int nd, Py_ssize_t *index, const Py_ssize_t *shape)
     }
 }
 
-void
+static void
 _Py_add_one_to_index_C(int nd, Py_ssize_t *index, const Py_ssize_t *shape)
 {
     int k;
diff --git a/Objects/descrobject.c b/Objects/descrobject.c
index 98d8698fa70..89bac99bb9d 100644
--- a/Objects/descrobject.c
+++ b/Objects/descrobject.c
@@ -1,6 +1,7 @@
 /* Descriptors -- a new, flexible way to describe attributes */
 
 #include "Python.h"
+#include "pycore_abstract.h"      // _PyObject_RealIsSubclass()
 #include "pycore_ceval.h"         // _Py_EnterRecursiveCallTstate()
 #include "pycore_object.h"        // _PyObject_GC_UNTRACK()
 #include "pycore_pystate.h"       // _PyThreadState_GET()
diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index f27e6f6c143..015dd27ec33 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -7,6 +7,7 @@
 #define PY_SSIZE_T_CLEAN
 #include <Python.h>
 #include <stdbool.h>
+#include "pycore_abstract.h"      // _PyObject_RealIsSubclass()
 #include "pycore_ceval.h"         // _Py_EnterRecursiveCall
 #include "pycore_pyerrors.h"      // struct _PyErr_SetRaisedException
 #include "pycore_exceptions.h"    // struct _Py_exc_state