diff --git a/Makefile.pre.in b/Makefile.pre.in
index 84c783327ed..c17c3d6067d 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -2568,7 +2568,7 @@ MODULE__SHA3_DEPS=$(srcdir)/Modules/_sha3/sha3.c $(srcdir)/Modules/_sha3/sha3.h
 MODULE__SHA512_DEPS=$(srcdir)/Modules/hashlib.h
 MODULE__SOCKET_DEPS=$(srcdir)/Modules/socketmodule.h
 MODULE__SSL_DEPS=$(srcdir)/Modules/_ssl.h $(srcdir)/Modules/_ssl/cert.c $(srcdir)/Modules/_ssl/debughelpers.c $(srcdir)/Modules/_ssl/misc.c $(srcdir)/Modules/_ssl_data.h $(srcdir)/Modules/_ssl_data_111.h $(srcdir)/Modules/_ssl_data_300.h $(srcdir)/Modules/socketmodule.h
-MODULE__TESTCAPI_DEPS=$(srcdir)/Modules/testcapi_long.h
+MODULE__TESTCAPI_DEPS=$(srcdir)/Modules/testcapi_long.h Modules/_testcapi/parts.h $(srcdir)/Modules/_testcapi/vectorcall.c
 MODULE__SQLITE3_DEPS=$(srcdir)/Modules/_sqlite/connection.h $(srcdir)/Modules/_sqlite/cursor.h $(srcdir)/Modules/_sqlite/microprotocols.h $(srcdir)/Modules/_sqlite/module.h $(srcdir)/Modules/_sqlite/prepare_protocol.h $(srcdir)/Modules/_sqlite/row.h $(srcdir)/Modules/_sqlite/util.h
 
 # IF YOU PUT ANYTHING HERE IT WILL GO AWAY
diff --git a/Modules/Setup.stdlib.in b/Modules/Setup.stdlib.in
index 7357aacd726..581a5c7f979 100644
--- a/Modules/Setup.stdlib.in
+++ b/Modules/Setup.stdlib.in
@@ -168,7 +168,7 @@
 @MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
 @MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c
-@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c
+@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c
 
 # Some testing modules MUST be built as shared libraries.
 *shared*
diff --git a/Modules/_testcapi/README.txt b/Modules/_testcapi/README.txt
new file mode 100644
index 00000000000..134b6efc638
--- /dev/null
+++ b/Modules/_testcapi/README.txt
@@ -0,0 +1,3 @@
+Tests in this directory are compiled into the _testcapi extension.
+The main file for the extension is Modules/_testcapimodule.c, which
+calls `_PyTestCapi_Init_*` from these functions.
diff --git a/Modules/_testcapi/parts.h b/Modules/_testcapi/parts.h
new file mode 100644
index 00000000000..1111021e185
--- /dev/null
+++ b/Modules/_testcapi/parts.h
@@ -0,0 +1,3 @@
+#include "Python.h"
+
+PyAPI_FUNC(int) _PyTestCapi_Init_Vectorcall(PyObject *module);
diff --git a/Modules/_testcapi/vectorcall.c b/Modules/_testcapi/vectorcall.c
new file mode 100644
index 00000000000..9bc702905ca
--- /dev/null
+++ b/Modules/_testcapi/vectorcall.c
@@ -0,0 +1,270 @@
+#include "parts.h"
+#include <stddef.h>  // offsetof
+
+
+/* Test PEP 590 - Vectorcall */
+
+static int
+fastcall_args(PyObject *args, PyObject ***stack, Py_ssize_t *nargs)
+{
+    if (args == Py_None) {
+        *stack = NULL;
+        *nargs = 0;
+    }
+    else if (PyTuple_Check(args)) {
+        *stack = ((PyTupleObject *)args)->ob_item;
+        *nargs = PyTuple_GET_SIZE(args);
+    }
+    else {
+        PyErr_SetString(PyExc_TypeError, "args must be None or a tuple");
+        return -1;
+    }
+    return 0;
+}
+
+
+static PyObject *
+test_pyobject_fastcall(PyObject *self, PyObject *args)
+{
+    PyObject *func, *func_args;
+    PyObject **stack;
+    Py_ssize_t nargs;
+
+    if (!PyArg_ParseTuple(args, "OO", &func, &func_args)) {
+        return NULL;
+    }
+
+    if (fastcall_args(func_args, &stack, &nargs) < 0) {
+        return NULL;
+    }
+    return _PyObject_FastCall(func, stack, nargs);
+}
+
+static PyObject *
+test_pyobject_fastcalldict(PyObject *self, PyObject *args)
+{
+    PyObject *func, *func_args, *kwargs;
+    PyObject **stack;
+    Py_ssize_t nargs;
+
+    if (!PyArg_ParseTuple(args, "OOO", &func, &func_args, &kwargs)) {
+        return NULL;
+    }
+
+    if (fastcall_args(func_args, &stack, &nargs) < 0) {
+        return NULL;
+    }
+
+    if (kwargs == Py_None) {
+        kwargs = NULL;
+    }
+    else if (!PyDict_Check(kwargs)) {
+        PyErr_SetString(PyExc_TypeError, "kwnames must be None or a dict");
+        return NULL;
+    }
+
+    return PyObject_VectorcallDict(func, stack, nargs, kwargs);
+}
+
+static PyObject *
+test_pyobject_vectorcall(PyObject *self, PyObject *args)
+{
+    PyObject *func, *func_args, *kwnames = NULL;
+    PyObject **stack;
+    Py_ssize_t nargs, nkw;
+
+    if (!PyArg_ParseTuple(args, "OOO", &func, &func_args, &kwnames)) {
+        return NULL;
+    }
+
+    if (fastcall_args(func_args, &stack, &nargs) < 0) {
+        return NULL;
+    }
+
+    if (kwnames == Py_None) {
+        kwnames = NULL;
+    }
+    else if (PyTuple_Check(kwnames)) {
+        nkw = PyTuple_GET_SIZE(kwnames);
+        if (nargs < nkw) {
+            PyErr_SetString(PyExc_ValueError, "kwnames longer than args");
+            return NULL;
+        }
+        nargs -= nkw;
+    }
+    else {
+        PyErr_SetString(PyExc_TypeError, "kwnames must be None or a tuple");
+        return NULL;
+    }
+    return PyObject_Vectorcall(func, stack, nargs, kwnames);
+}
+
+static PyObject *
+test_pyvectorcall_call(PyObject *self, PyObject *args)
+{
+    PyObject *func;
+    PyObject *argstuple;
+    PyObject *kwargs = NULL;
+
+    if (!PyArg_ParseTuple(args, "OO|O", &func, &argstuple, &kwargs)) {
+        return NULL;
+    }
+
+    if (!PyTuple_Check(argstuple)) {
+        PyErr_SetString(PyExc_TypeError, "args must be a tuple");
+        return NULL;
+    }
+    if (kwargs != NULL && !PyDict_Check(kwargs)) {
+        PyErr_SetString(PyExc_TypeError, "kwargs must be a dict");
+        return NULL;
+    }
+
+    return PyVectorcall_Call(func, argstuple, kwargs);
+}
+
+static PyMethodDef TestMethods[] = {
+    {"pyobject_fastcall", test_pyobject_fastcall, METH_VARARGS},
+    {"pyobject_fastcalldict", test_pyobject_fastcalldict, METH_VARARGS},
+    {"pyobject_vectorcall", test_pyobject_vectorcall, METH_VARARGS},
+    {"pyvectorcall_call", test_pyvectorcall_call, METH_VARARGS},
+    {NULL},
+};
+
+
+typedef struct {
+    PyObject_HEAD
+    vectorcallfunc vectorcall;
+} MethodDescriptorObject;
+
+static PyObject *
+MethodDescriptor_vectorcall(PyObject *callable, PyObject *const *args,
+                            size_t nargsf, PyObject *kwnames)
+{
+    /* True if using the vectorcall function in MethodDescriptorObject
+     * but False for MethodDescriptor2Object */
+    MethodDescriptorObject *md = (MethodDescriptorObject *)callable;
+    return PyBool_FromLong(md->vectorcall != NULL);
+}
+
+static PyObject *
+MethodDescriptor_new(PyTypeObject* type, PyObject* args, PyObject *kw)
+{
+    MethodDescriptorObject *op = (MethodDescriptorObject *)type->tp_alloc(type, 0);
+    op->vectorcall = MethodDescriptor_vectorcall;
+    return (PyObject *)op;
+}
+
+static PyObject *
+func_descr_get(PyObject *func, PyObject *obj, PyObject *type)
+{
+    if (obj == Py_None || obj == NULL) {
+        Py_INCREF(func);
+        return func;
+    }
+    return PyMethod_New(func, obj);
+}
+
+static PyObject *
+nop_descr_get(PyObject *func, PyObject *obj, PyObject *type)
+{
+    Py_INCREF(func);
+    return func;
+}
+
+static PyObject *
+call_return_args(PyObject *self, PyObject *args, PyObject *kwargs)
+{
+    Py_INCREF(args);
+    return args;
+}
+
+static PyTypeObject MethodDescriptorBase_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "MethodDescriptorBase",
+    sizeof(MethodDescriptorObject),
+    .tp_new = MethodDescriptor_new,
+    .tp_call = PyVectorcall_Call,
+    .tp_vectorcall_offset = offsetof(MethodDescriptorObject, vectorcall),
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+                Py_TPFLAGS_METHOD_DESCRIPTOR | Py_TPFLAGS_HAVE_VECTORCALL,
+    .tp_descr_get = func_descr_get,
+};
+
+static PyTypeObject MethodDescriptorDerived_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "MethodDescriptorDerived",
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
+};
+
+static PyTypeObject MethodDescriptorNopGet_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "MethodDescriptorNopGet",
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
+    .tp_call = call_return_args,
+    .tp_descr_get = nop_descr_get,
+};
+
+typedef struct {
+    MethodDescriptorObject base;
+    vectorcallfunc vectorcall;
+} MethodDescriptor2Object;
+
+static PyObject *
+MethodDescriptor2_new(PyTypeObject* type, PyObject* args, PyObject *kw)
+{
+    MethodDescriptor2Object *op = PyObject_New(MethodDescriptor2Object, type);
+    op->base.vectorcall = NULL;
+    op->vectorcall = MethodDescriptor_vectorcall;
+    return (PyObject *)op;
+}
+
+static PyTypeObject MethodDescriptor2_Type = {
+    PyVarObject_HEAD_INIT(NULL, 0)
+    "MethodDescriptor2",
+    sizeof(MethodDescriptor2Object),
+    .tp_new = MethodDescriptor2_new,
+    .tp_call = PyVectorcall_Call,
+    .tp_vectorcall_offset = offsetof(MethodDescriptor2Object, vectorcall),
+    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_VECTORCALL,
+};
+
+
+int
+_PyTestCapi_Init_Vectorcall(PyObject *m) {
+    if (PyModule_AddFunctions(m, TestMethods) < 0) {
+        return -1;
+    }
+
+    if (PyType_Ready(&MethodDescriptorBase_Type) < 0) {
+        return -1;
+    }
+    if (PyModule_AddType(m, &MethodDescriptorBase_Type) < 0) {
+        return -1;
+    }
+
+    MethodDescriptorDerived_Type.tp_base = &MethodDescriptorBase_Type;
+    if (PyType_Ready(&MethodDescriptorDerived_Type) < 0) {
+        return -1;
+    }
+    if (PyModule_AddType(m, &MethodDescriptorDerived_Type) < 0) {
+        return -1;
+    }
+
+    MethodDescriptorNopGet_Type.tp_base = &MethodDescriptorBase_Type;
+    if (PyType_Ready(&MethodDescriptorNopGet_Type) < 0) {
+        return -1;
+    }
+    if (PyModule_AddType(m, &MethodDescriptorNopGet_Type) < 0) {
+        return -1;
+    }
+
+    MethodDescriptor2_Type.tp_base = &MethodDescriptorBase_Type;
+    if (PyType_Ready(&MethodDescriptor2_Type) < 0) {
+        return -1;
+    }
+    if (PyModule_AddType(m, &MethodDescriptor2_Type) < 0) {
+        return -1;
+    }
+
+    return 0;
+}
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index 7d88f4f51f8..436c701a7a3 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -43,6 +43,10 @@
 #  error "The public headers should not include <stdbool.h>, see bpo-46748"
 #endif
 
+// Several parts of this module are broken out into files in _testcapi/.
+// Include definitions from there.
+#include "_testcapi/parts.h"
+
 // Forward declarations
 static struct PyModuleDef _testcapimodule;
 static PyType_Spec HeapTypeNameType_Spec;
@@ -5299,128 +5303,6 @@ raise_SIGINT_then_send_None(PyObject *self, PyObject *args)
 }
 
 
-static int
-fastcall_args(PyObject *args, PyObject ***stack, Py_ssize_t *nargs)
-{
-    if (args == Py_None) {
-        *stack = NULL;
-        *nargs = 0;
-    }
-    else if (PyTuple_Check(args)) {
-        *stack = ((PyTupleObject *)args)->ob_item;
-        *nargs = PyTuple_GET_SIZE(args);
-    }
-    else {
-        PyErr_SetString(PyExc_TypeError, "args must be None or a tuple");
-        return -1;
-    }
-    return 0;
-}
-
-
-static PyObject *
-test_pyobject_fastcall(PyObject *self, PyObject *args)
-{
-    PyObject *func, *func_args;
-    PyObject **stack;
-    Py_ssize_t nargs;
-
-    if (!PyArg_ParseTuple(args, "OO", &func, &func_args)) {
-        return NULL;
-    }
-
-    if (fastcall_args(func_args, &stack, &nargs) < 0) {
-        return NULL;
-    }
-    return _PyObject_FastCall(func, stack, nargs);
-}
-
-
-static PyObject *
-test_pyobject_fastcalldict(PyObject *self, PyObject *args)
-{
-    PyObject *func, *func_args, *kwargs;
-    PyObject **stack;
-    Py_ssize_t nargs;
-
-    if (!PyArg_ParseTuple(args, "OOO", &func, &func_args, &kwargs)) {
-        return NULL;
-    }
-
-    if (fastcall_args(func_args, &stack, &nargs) < 0) {
-        return NULL;
-    }
-
-    if (kwargs == Py_None) {
-        kwargs = NULL;
-    }
-    else if (!PyDict_Check(kwargs)) {
-        PyErr_SetString(PyExc_TypeError, "kwnames must be None or a dict");
-        return NULL;
-    }
-
-    return PyObject_VectorcallDict(func, stack, nargs, kwargs);
-}
-
-
-static PyObject *
-test_pyobject_vectorcall(PyObject *self, PyObject *args)
-{
-    PyObject *func, *func_args, *kwnames = NULL;
-    PyObject **stack;
-    Py_ssize_t nargs, nkw;
-
-    if (!PyArg_ParseTuple(args, "OOO", &func, &func_args, &kwnames)) {
-        return NULL;
-    }
-
-    if (fastcall_args(func_args, &stack, &nargs) < 0) {
-        return NULL;
-    }
-
-    if (kwnames == Py_None) {
-        kwnames = NULL;
-    }
-    else if (PyTuple_Check(kwnames)) {
-        nkw = PyTuple_GET_SIZE(kwnames);
-        if (nargs < nkw) {
-            PyErr_SetString(PyExc_ValueError, "kwnames longer than args");
-            return NULL;
-        }
-        nargs -= nkw;
-    }
-    else {
-        PyErr_SetString(PyExc_TypeError, "kwnames must be None or a tuple");
-        return NULL;
-    }
-    return PyObject_Vectorcall(func, stack, nargs, kwnames);
-}
-
-
-static PyObject *
-test_pyvectorcall_call(PyObject *self, PyObject *args)
-{
-    PyObject *func;
-    PyObject *argstuple;
-    PyObject *kwargs = NULL;
-
-    if (!PyArg_ParseTuple(args, "OO|O", &func, &argstuple, &kwargs)) {
-        return NULL;
-    }
-
-    if (!PyTuple_Check(argstuple)) {
-        PyErr_SetString(PyExc_TypeError, "args must be a tuple");
-        return NULL;
-    }
-    if (kwargs != NULL && !PyDict_Check(kwargs)) {
-        PyErr_SetString(PyExc_TypeError, "kwargs must be a dict");
-        return NULL;
-    }
-
-    return PyVectorcall_Call(func, argstuple, kwargs);
-}
-
-
 static PyObject*
 stack_pointer(PyObject *self, PyObject *args)
 {
@@ -6403,10 +6285,6 @@ static PyMethodDef TestMethods[] = {
     {"tracemalloc_get_traceback", tracemalloc_get_traceback, METH_VARARGS},
     {"dict_get_version", dict_get_version, METH_VARARGS},
     {"raise_SIGINT_then_send_None", raise_SIGINT_then_send_None, METH_VARARGS},
-    {"pyobject_fastcall", test_pyobject_fastcall, METH_VARARGS},
-    {"pyobject_fastcalldict", test_pyobject_fastcalldict, METH_VARARGS},
-    {"pyobject_vectorcall", test_pyobject_vectorcall, METH_VARARGS},
-    {"pyvectorcall_call", test_pyvectorcall_call, METH_VARARGS},
     {"stack_pointer", stack_pointer, METH_NOARGS},
 #ifdef W_STOPCODE
     {"W_STOPCODE", py_w_stopcode, METH_VARARGS},
@@ -7009,106 +6887,6 @@ static PyTypeObject Generic_Type = {
     .tp_methods = generic_methods,
 };
 
-
-/* Test PEP 590 */
-
-typedef struct {
-    PyObject_HEAD
-    vectorcallfunc vectorcall;
-} MethodDescriptorObject;
-
-static PyObject *
-MethodDescriptor_vectorcall(PyObject *callable, PyObject *const *args,
-                            size_t nargsf, PyObject *kwnames)
-{
-    /* True if using the vectorcall function in MethodDescriptorObject
-     * but False for MethodDescriptor2Object */
-    MethodDescriptorObject *md = (MethodDescriptorObject *)callable;
-    return PyBool_FromLong(md->vectorcall != NULL);
-}
-
-static PyObject *
-MethodDescriptor_new(PyTypeObject* type, PyObject* args, PyObject *kw)
-{
-    MethodDescriptorObject *op = (MethodDescriptorObject *)type->tp_alloc(type, 0);
-    op->vectorcall = MethodDescriptor_vectorcall;
-    return (PyObject *)op;
-}
-
-static PyObject *
-func_descr_get(PyObject *func, PyObject *obj, PyObject *type)
-{
-    if (obj == Py_None || obj == NULL) {
-        Py_INCREF(func);
-        return func;
-    }
-    return PyMethod_New(func, obj);
-}
-
-static PyObject *
-nop_descr_get(PyObject *func, PyObject *obj, PyObject *type)
-{
-    Py_INCREF(func);
-    return func;
-}
-
-static PyObject *
-call_return_args(PyObject *self, PyObject *args, PyObject *kwargs)
-{
-    Py_INCREF(args);
-    return args;
-}
-
-static PyTypeObject MethodDescriptorBase_Type = {
-    PyVarObject_HEAD_INIT(NULL, 0)
-    "MethodDescriptorBase",
-    sizeof(MethodDescriptorObject),
-    .tp_new = MethodDescriptor_new,
-    .tp_call = PyVectorcall_Call,
-    .tp_vectorcall_offset = offsetof(MethodDescriptorObject, vectorcall),
-    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
-                Py_TPFLAGS_METHOD_DESCRIPTOR | Py_TPFLAGS_HAVE_VECTORCALL,
-    .tp_descr_get = func_descr_get,
-};
-
-static PyTypeObject MethodDescriptorDerived_Type = {
-    PyVarObject_HEAD_INIT(NULL, 0)
-    "MethodDescriptorDerived",
-    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
-};
-
-static PyTypeObject MethodDescriptorNopGet_Type = {
-    PyVarObject_HEAD_INIT(NULL, 0)
-    "MethodDescriptorNopGet",
-    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
-    .tp_call = call_return_args,
-    .tp_descr_get = nop_descr_get,
-};
-
-typedef struct {
-    MethodDescriptorObject base;
-    vectorcallfunc vectorcall;
-} MethodDescriptor2Object;
-
-static PyObject *
-MethodDescriptor2_new(PyTypeObject* type, PyObject* args, PyObject *kw)
-{
-    MethodDescriptor2Object *op = PyObject_New(MethodDescriptor2Object, type);
-    op->base.vectorcall = NULL;
-    op->vectorcall = MethodDescriptor_vectorcall;
-    return (PyObject *)op;
-}
-
-static PyTypeObject MethodDescriptor2_Type = {
-    PyVarObject_HEAD_INIT(NULL, 0)
-    "MethodDescriptor2",
-    sizeof(MethodDescriptor2Object),
-    .tp_new = MethodDescriptor2_new,
-    .tp_call = PyVectorcall_Call,
-    .tp_vectorcall_offset = offsetof(MethodDescriptor2Object, vectorcall),
-    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_VECTORCALL,
-};
-
 PyDoc_STRVAR(heapdocctype__doc__,
 "HeapDocCType(arg1, arg2)\n"
 "--\n"
@@ -7778,29 +7556,6 @@ PyInit__testcapi(void)
     Py_INCREF(&MyList_Type);
     PyModule_AddObject(m, "MyList", (PyObject *)&MyList_Type);
 
-    if (PyType_Ready(&MethodDescriptorBase_Type) < 0)
-        return NULL;
-    Py_INCREF(&MethodDescriptorBase_Type);
-    PyModule_AddObject(m, "MethodDescriptorBase", (PyObject *)&MethodDescriptorBase_Type);
-
-    MethodDescriptorDerived_Type.tp_base = &MethodDescriptorBase_Type;
-    if (PyType_Ready(&MethodDescriptorDerived_Type) < 0)
-        return NULL;
-    Py_INCREF(&MethodDescriptorDerived_Type);
-    PyModule_AddObject(m, "MethodDescriptorDerived", (PyObject *)&MethodDescriptorDerived_Type);
-
-    MethodDescriptorNopGet_Type.tp_base = &MethodDescriptorBase_Type;
-    if (PyType_Ready(&MethodDescriptorNopGet_Type) < 0)
-        return NULL;
-    Py_INCREF(&MethodDescriptorNopGet_Type);
-    PyModule_AddObject(m, "MethodDescriptorNopGet", (PyObject *)&MethodDescriptorNopGet_Type);
-
-    MethodDescriptor2_Type.tp_base = &MethodDescriptorBase_Type;
-    if (PyType_Ready(&MethodDescriptor2_Type) < 0)
-        return NULL;
-    Py_INCREF(&MethodDescriptor2_Type);
-    PyModule_AddObject(m, "MethodDescriptor2", (PyObject *)&MethodDescriptor2_Type);
-
     if (PyType_Ready(&GenericAlias_Type) < 0)
         return NULL;
     Py_INCREF(&GenericAlias_Type);
@@ -7973,6 +7728,11 @@ PyInit__testcapi(void)
                            (PyObject *) &ContainerNoGC_type) < 0)
         return NULL;
 
+    /* Include tests from the _testcapi/ directory */
+    if (_PyTestCapi_Init_Vectorcall(m) < 0) {
+        return NULL;
+    }
+
     PyState_AddModule(m, &_testcapimodule);
     return m;
 }
@@ -8024,7 +7784,6 @@ test_buildvalue_issue38913(PyObject *self, PyObject *Py_UNUSED(ignored))
     }
     PyErr_Clear();
 
-
     Py_RETURN_NONE;
 }
 
diff --git a/PCbuild/_testcapi.vcxproj b/PCbuild/_testcapi.vcxproj
index c1a19437253..07e23557e1d 100644
--- a/PCbuild/_testcapi.vcxproj
+++ b/PCbuild/_testcapi.vcxproj
@@ -94,6 +94,7 @@
   </PropertyGroup>
   <ItemGroup>
     <ClCompile Include="..\Modules\_testcapimodule.c" />
+    <ClCompile Include="..\Modules\_testcapi\vectorcall.c" />
   </ItemGroup>
   <ItemGroup>
     <ResourceCompile Include="..\PC\python_nt.rc" />
diff --git a/PCbuild/_testcapi.vcxproj.filters b/PCbuild/_testcapi.vcxproj.filters
index 53f64b7aa1e..82fce057e2e 100644
--- a/PCbuild/_testcapi.vcxproj.filters
+++ b/PCbuild/_testcapi.vcxproj.filters
@@ -12,6 +12,9 @@
     <ClCompile Include="..\Modules\_testcapimodule.c">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="..\Modules\_testcapi\vectorcall.c">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ResourceCompile Include="..\PC\python_nt.rc">
diff --git a/setup.py b/setup.py
index 2edcb08b4fd..7c71ac6ec64 100644
--- a/setup.py
+++ b/setup.py
@@ -994,7 +994,7 @@ class PyBuildExt(build_ext):
 
     def detect_test_extensions(self):
         # Python C API test module
-        self.addext(Extension('_testcapi', ['_testcapimodule.c']))
+        self.addext(Extension('_testcapi', ['_testcapimodule.c', '_testcapi/vectorcall.c']))
 
         # Python Internal C API test module
         self.addext(Extension('_testinternalcapi', ['_testinternalcapi.c']))