diff --git a/Lib/test/test_pyexpat.py b/Lib/test/test_pyexpat.py
--- a/Lib/test/test_pyexpat.py
+++ b/Lib/test/test_pyexpat.py
@@ -641,6 +641,16 @@
parser.Parse("")
self.assertEqual(handler_call_args, [(None, None)])
+ # test UseForeignDTD() is equal to UseForeignDTD(True)
+ handler_call_args[:] = []
+
+ parser = expat.ParserCreate()
+ parser.UseForeignDTD()
+ parser.SetParamEntityParsing(expat.XML_PARAM_ENTITY_PARSING_ALWAYS)
+ parser.ExternalEntityRefHandler = resolve_entity
+ parser.Parse("")
+ self.assertEqual(handler_call_args, [(None, None)])
+
def test_ignore_use_foreign_dtd(self):
"""
If UseForeignDTD is passed True and a document with an external
diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -1035,7 +1035,7 @@
PyObject *flagobj = NULL;
int flag = 1;
enum XML_Error rc;
- if (!PyArg_ParseTuple(args, "O:UseForeignDTD", &flagobj))
+ if (!PyArg_ParseTuple(args, "|O:UseForeignDTD", &flagobj))
return NULL;
if (flagobj != NULL) {
flag = PyObject_IsTrue(flagobj);