diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -6621,7 +6621,7 @@ posix_confstr(PyObject *self, PyObject *
 {
     PyObject *result = NULL;
     int name;
-    char buffer[256];
+    char buffer[1];
 
     if (PyArg_ParseTuple(args, "O&:confstr", conv_confstr_confname, &name)) {
         int len;