diff --git a/Modules/cStringIO.c b/Modules/cStringIO.c
index 068a8354137..1dbec846516 100644
--- a/Modules/cStringIO.c
+++ b/Modules/cStringIO.c
@@ -376,7 +376,7 @@ O_write(Oobject *self, PyObject *args) {
         char *c;
         int l;
 
-        UNLESS (PyArg_ParseTuple(args, "s#:write", &c, &l)) return NULL;
+        UNLESS (PyArg_ParseTuple(args, "t#:write", &c, &l)) return NULL;
 
         if (O_cwrite((PyObject*)self,c,l) < 0) return NULL;