diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -3064,6 +3064,106 @@
 #endif   /* WITH_THREAD */
 
 
+/* StructSequence */
+static PyStructSequence_Field struct_unnamed_end_fields[] = {
+    {"a", "letter"},
+    {"b", "letter"},
+    {"c", "letter"},
+    {NULL, NULL},
+    {NULL, NULL},
+    {0}
+};
+
+static PyStructSequence_Field struct_unnamed_middle_fields[] = {
+    {"a", "letter"},
+    {NULL, NULL},
+    {NULL, NULL},
+    {"b", "letter"},
+    {"c", "letter"},
+    {0}
+};
+
+static PyStructSequence_Field struct_unnamed_alternating_fields[] = {
+    {"a", "letter"},
+    {NULL, NULL},
+    {"b", "letter"},
+    {NULL, NULL},
+    {"c", "letter"},
+    {0}
+};
+
+#define STRUCTSEQ_LEN 5
+
+static PyStructSequence_Desc struct_unnamed_end_desc = {
+    "_testcapi.struct_unnamed_end",
+    "structseq with an unnamed block at the end",
+    struct_unnamed_end_fields,
+    STRUCTSEQ_LEN,
+};
+
+static PyStructSequence_Desc struct_unnamed_middle_desc = {
+    "_testcapi.struct_unnamed_middle",
+    "structseq with an unnamed block in the middle",
+    struct_unnamed_middle_fields,
+    STRUCTSEQ_LEN,
+};
+
+static PyStructSequence_Desc struct_unnamed_alternating_desc = {
+    "_testcapi.struct_unnamed_alternating",
+    "structseq with alternating named/unnamed fields",
+    struct_unnamed_alternating_fields,
+    STRUCTSEQ_LEN,
+};
+
+static int structseq_initialized = 0;
+static PyTypeObject StructUnnamedEndType;
+static PyTypeObject StructUnnamedMiddleType;
+static PyTypeObject StructUnnamedAlternatingType;
+
+#define SET(i,val) PyStructSequence_SET_ITEM(v, i, PyLong_FromLong((long) val))
+static PyObject *
+mk_structseq(PyObject *self, PyObject *args)
+{
+    PyObject *v;
+    char *s;
+
+    if (!PyArg_ParseTuple(args, "s", &s)) {
+        return NULL;
+    }
+
+    if (strcmp(s, "unnamed_end") == 0) {
+        v = PyStructSequence_New(&StructUnnamedEndType);
+    }
+    else if (strcmp(s, "unnamed_middle") == 0) {
+        v = PyStructSequence_New(&StructUnnamedMiddleType);
+    }
+    else if (strcmp(s, "unnamed_alternating") == 0) {
+        v = PyStructSequence_New(&StructUnnamedAlternatingType);
+    }
+    else {
+        PyErr_SetString(PyExc_ValueError,
+            "mk_structseq: invalid structseq type");
+        return NULL;
+    }
+
+    if (v == NULL)
+        return NULL;
+
+    SET(0, 0);
+    SET(1, 1);
+    SET(2, 2);
+    SET(3, 3);
+    SET(4, 4);
+
+    if (PyErr_Occurred()) {
+        Py_XDECREF(v);
+        return NULL;
+    }
+
+    return v;
+}
+
+
 static PyMethodDef TestMethods[] = {
     {"raise_exception",         raise_exception,                 METH_VARARGS},
     {"raise_memoryerror",   (PyCFunction)raise_memoryerror,  METH_NOARGS},
@@ -3198,6 +3298,7 @@
     {"docstring_with_signature_with_defaults",
         (PyCFunction)test_with_docstring, METH_NOARGS,
         docstring_with_signature_with_defaults},
+    {"mk_structseq", mk_structseq,  METH_VARARGS, "make a struct sequence"},
 #ifdef WITH_THREAD
     {"call_in_temporary_c_thread", call_in_temporary_c_thread, METH_O,
      PyDoc_STR("set_error_class(error_class) -> None")},
@@ -3481,11 +3582,38 @@
 PyInit__testcapi(void)
 {
     PyObject *m;
+    int i;
 
     m = PyModule_Create(&_testcapimodule);
     if (m == NULL)
         return NULL;
 
+    if (!structseq_initialized) {
+        for (i = 0; i < STRUCTSEQ_LEN; i++) {
+            if (struct_unnamed_end_fields[i].name == NULL) {
+                struct_unnamed_end_fields[i].name = PyStructSequence_UnnamedField;
+            }
+            if (struct_unnamed_middle_fields[i].name == NULL) {
+                struct_unnamed_middle_fields[i].name = PyStructSequence_UnnamedField;
+            }
+            if (struct_unnamed_alternating_fields[i].name == NULL) {
+                struct_unnamed_alternating_fields[i].name = PyStructSequence_UnnamedField;
+            }
+        }
+        if (PyStructSequence_InitType2(&StructUnnamedEndType,
+                                       &struct_unnamed_end_desc) < 0) {
+            return NULL;
+        }
+        if (PyStructSequence_InitType2(&StructUnnamedMiddleType,
+                                       &struct_unnamed_middle_desc) < 0) {
+            return NULL;
+        }
+        if (PyStructSequence_InitType2(&StructUnnamedAlternatingType,
+                                       &struct_unnamed_alternating_desc) < 0) {
+            return NULL;
+        }
+    }
+
     Py_TYPE(&_HashInheritanceTester_Type)=&PyType_Type;
 
     Py_TYPE(&test_structmembersType)=&PyType_Type;