Index: Modules/posixmodule.c
===================================================================
--- Modules/posixmodule.c	(revision 66545)
+++ Modules/posixmodule.c	(working copy)
@@ -2326,7 +2326,7 @@
 	PyObject *d, *v;
 	DIR *dirp;
 	struct dirent *ep;
-	int arg_is_unicode = 1;
+	int arg_is_unicode = 1, problems = 0;
 
 	errno = 0;
 	if (!PyArg_ParseTuple(args, "U:listdir", &v)) {
@@ -2378,9 +2378,9 @@
 				v = w;
 			}
 			else {
-				/* fall back to the original byte string, as
-				   discussed in patch #683592 */
 				PyErr_Clear();
+				problems = 1;
+				continue;
 			}
 		}
 		if (PyList_Append(d, v) != 0) {
@@ -2394,6 +2394,13 @@
 	closedir(dirp);
 	PyMem_Free(name);
 
+	if (problems && PyErr_WarnEx(PyExc_UnicodeWarning,
+				     "Some file names could not be decoded "
+				     "and were ignored.", 2)) {
+		Py_DECREF(d);
+		return NULL;
+	}
+
 	return d;
 
 #endif /* which OS */