diff --git a/Lib/test/test_set.py b/Lib/test/test_set.py
index 26977d9..194bbff 100644
--- a/Lib/test/test_set.py
+++ b/Lib/test/test_set.py
@@ -607,7 +607,7 @@
     # C API test only available in a debug build
     if hasattr(set, "test_c_api"):
         def test_c_api(self):
-            self.assertEqual(set('abc').test_c_api(), True)
+            self.assertEqual(set().test_c_api(), True)
 
 class SetSubclass(set):
     pass
diff --git a/Objects/setobject.c b/Objects/setobject.c
index 7ea8e32..c3eabf5 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -2360,11 +2360,25 @@
 	PyObject *elem=NULL, *dup=NULL, *t, *f, *dup2, *x;
 	PyObject *ob = (PyObject *)so;
 	long hash;
+	PyObject *str;
 
-	/* Verify preconditions and exercise type/size checks */
+	/* Verify preconditions */
 	assert(PyAnySet_Check(ob));
 	assert(PyAnySet_CheckExact(ob));
 	assert(!PyFrozenSet_CheckExact(ob));
+
+	/* so.clear(); so |= set("abc"); */
+	str = PyUnicode_FromString("abc");
+	if (str == NULL)
+		return NULL;
+	set_clear_internal(so);
+	if (set_update_internal(so, str) == -1) {
+		Py_DECREF(str);
+		return NULL;
+	}
+	Py_DECREF(str);
+
+	/* Exercise type/size checks */
 	assert(PySet_Size(ob) == 3);
 	assert(PySet_GET_SIZE(ob) == 3);