diff -r 6ced540a92bc Modules/posixmodule.c
--- a/Modules/posixmodule.c	Wed Dec 21 14:08:55 2016 +0200
+++ b/Modules/posixmodule.c	Wed Dec 21 17:06:24 2016 +0200
@@ -998,11 +998,13 @@ path_converter(PyObject *o, void *p)
         goto exit;
     }
 
+    Py_XDECREF(to_cleanup);
+    to_cleanup = bytes;
+
     length = PyBytes_GET_SIZE(bytes);
     narrow = PyBytes_AS_STRING(bytes);
     if ((size_t)length != strlen(narrow)) {
         FORMAT_EXCEPTION(PyExc_ValueError, "embedded null character in %s");
-        Py_DECREF(bytes);
         goto exit;
     }
 
@@ -1039,10 +1041,10 @@ path_converter(PyObject *o, void *p)
     path->object = o;
     path->fd = -1;
     if (bytes == o) {
-        Py_DECREF(bytes);
         ret = 1;
     }
     else {
+        to_cleanup = NULL;
         path->cleanup = bytes;
         ret = Py_CLEANUP_SUPPORTED;
     }