Index: Lib/test/test_struct.py
===================================================================
--- Lib/test/test_struct.py	(revision 78756)
+++ Lib/test/test_struct.py	(working copy)
@@ -6,7 +6,7 @@
                         DeprecationWarning)
 
 from functools import wraps
-from test.test_support import run_unittest
+from test.test_support import run_unittest, check_warnings
 
 import sys
 ISBIGENDIAN = sys.byteorder == "big"
@@ -291,17 +291,29 @@
 
                 class NotAnIntOS:
                     def __int__(self):
-                        return 10585
+                        return 85
 
                     def __long__(self):
                         return -163L
 
-                for badobject in ("a string", 3+42j, randrange,
-                                  NotAnIntNS(), NotAnIntOS()):
-                    self.assertRaises(struct.error,
-                                      struct.pack, format,
+                for badobject in ("a string", 3+42j, randrange):
+                    self.assertRaises((TypeError, struct.error),
+                                      struct.pack, self.format,
                                       badobject)
 
+                # check that attempts to convert non-integers produce
+                # a DeprecationWarning
+                for nonint in NotAnIntNS(), NotAnIntOS():
+                    with check_warnings() as w:
+                        warnings.simplefilter(
+                            action="always",
+                            category=DeprecationWarning
+                            )
+                        self.assertEqual(struct.pack(self.format, nonint),
+                                         struct.pack(self.format, int(nonint)))
+                        self.assertEqual(w.category, DeprecationWarning)
+                        self.assertIn("got non-integer", str(w.message))
+
         byteorders = '', '@', '=', '<', '>', '!'
         for code in integer_codes:
             for byteorder in byteorders:
Index: Modules/_struct.c
===================================================================
--- Modules/_struct.c	(revision 78756)
+++ Modules/_struct.c	(working copy)
@@ -17,7 +17,10 @@
 typedef int Py_ssize_t;
 #endif
 
-#define FLOAT_COERCE "integer argument expected, got float"
+/* warning messages */
+#define FLOAT_COERCE_WARN "integer argument expected, got float"
+#define NON_INTEGER_WARN "integer argument expected, got non-integer " \
+	"(implicit conversion using __int__ is deprecated)"
 
 
 /* The translation function for each format character is table driven */
@@ -104,21 +107,57 @@
 static PyObject *
 get_pylong(PyObject *v)
 {
+	PyObject *r;
 	assert(v != NULL);
-	if (PyInt_Check(v))
-		return PyLong_FromLong(PyInt_AS_LONG(v));
-	if (PyLong_Check(v)) {
+	if (!PyInt_Check(v) && !PyLong_Check(v)) {
+		PyNumberMethods *m;
+		/* Not an integer; try to use __int__ to convert to an
+		   integer.  This behaviour is deprecated, and is removed in
+		   Python 3.x. */
+		m = Py_TYPE(v)->tp_as_number;
+		if (m != NULL && m->nb_int != NULL) {
+			/* Special case warning message for floats, for
+			   backwards compatibility. */
+			if (PyFloat_Check(v)) {
+				if (PyErr_WarnEx(PyExc_DeprecationWarning,
+						 FLOAT_COERCE_WARN, 1))
+					return NULL;
+			}
+			else {
+				if (PyErr_WarnEx(PyExc_DeprecationWarning,
+						 NON_INTEGER_WARN, 1))
+					return NULL;
+			}
+			v = m->nb_int(v);
+			if (v == NULL)
+				return NULL;
+			if (!PyInt_Check(v) && !PyLong_Check(v)) {
+				PyErr_SetString(PyExc_TypeError,
+				  "__int__ method returned non-integer");
+			}
+		}
+		else {
+			PyErr_SetString(StructError,
+					"cannot convert argument to integer");
+			return NULL;
+		}
+	}
+	else
+		/* Ensure we own a reference to v. */
 		Py_INCREF(v);
-		return v;
+
+	if (PyInt_Check(v)) {
+		r = PyLong_FromLong(PyInt_AS_LONG(v));
+		Py_DECREF(v);
 	}
-	if (PyFloat_Check(v)) {
-		if (PyErr_WarnEx(PyExc_DeprecationWarning, FLOAT_COERCE, 1)<0)
-			return NULL;
-		return PyNumber_Long(v);
+	else if (PyLong_Check(v)) {
+		assert(PyLong_Check(v));
+		r = v;
 	}
-	PyErr_SetString(StructError,
-			"cannot convert argument to long");
-	return NULL;
+	else
+		assert(0);  /* shouldn't ever get here */
+
+	return r;
 }
 
 /* Helper to convert a Python object to a C long.  Sets an exception