diff -r c144bf6c0ff7 Lib/test/test_builtin.py
--- a/Lib/test/test_builtin.py	Thu Jan 19 19:38:13 2017 +0200
+++ b/Lib/test/test_builtin.py	Thu Jan 19 20:26:32 2017 +0200
@@ -1627,6 +1627,16 @@ class TestSorted(unittest.TestCase):
         self.assertEqual(data, sorted(copy, reverse=1))
         self.assertNotEqual(data, copy)
 
+    def test_bad_arguments(self):
+        # Issue #29327: The first argument is positional-only.
+        sorted([])
+        with self.assertRaises(TypeError):
+            sorted(iterable=[])
+        # Other arguments are keyword-only
+        sorted([], key=None)
+        with self.assertRaises(TypeError):
+            sorted([], None)
+
     def test_inputtypes(self):
         s = 'abracadabra'
         types = [list, tuple, str]
diff -r c144bf6c0ff7 Python/bltinmodule.c
--- a/Python/bltinmodule.c	Thu Jan 19 19:38:13 2017 +0200
+++ b/Python/bltinmodule.c	Thu Jan 19 20:26:32 2017 +0200
@@ -2128,7 +2128,7 @@ builtin_sorted(PyObject *self, PyObject 
 {
     PyObject *newlist, *v, *seq, *keyfunc=NULL;
     PyObject *callable;
-    static const char * const kwlist[] = {"iterable", "key", "reverse", 0};
+    static const char * const kwlist[] = {"", "key", "reverse", 0};
     /* args 1-3 should match listsort in Objects/listobject.c */
     static _PyArg_Parser parser = {"O|Oi:sorted", kwlist, 0};
     int reverse;
@@ -2147,6 +2147,7 @@ builtin_sorted(PyObject *self, PyObject 
         return NULL;
     }
 
+    assert(nargs >= 1);
     v = _PyObject_FastCallKeywords(callable, args + 1, nargs - 1, kwnames);
     Py_DECREF(callable);
     if (v == NULL) {