Use 'S' format character for the optional constructor argument, so we

get a decent error message when it's not a string (instead of
confusing errors when trying to use the thing).

1 files changed, 1 insertions, 1 deletions

diff --git a/Modules/cStringIO.c b/Modules/cStringIO.c
index 2d7c940c08..494d895d3d 100644
--- a/Modules/cStringIO.c
+++ b/Modules/cStringIO.c
@@ -565,7 +565,7 @@ static PyObject *
 IO_StringIO(PyObject *self, PyObject *args) {
   PyObject *s=0;
 
-  UNLESS(PyArg_ParseTuple(args, "|O", &s)) return NULL;
+  UNLESS(PyArg_ParseTuple(args, "|S", &s)) return NULL;
   if(s) return newIobject(s);
   return newOobject(128);
 }