#4783: document that is not possible to use json.dump twice on the same stream.
diff --git a/Doc/library/json.rst b/Doc/library/json.rst
index 2bf242f..0b42012 100644
--- a/Doc/library/json.rst
+++ b/Doc/library/json.rst
@@ -156,6 +156,11 @@
Serialize *obj* to a JSON formatted :class:`str`. The arguments have the
same meaning as in :func:`dump`.
+ .. note::
+
+ Unlike :mod:`pickle` and :mod:`marshal`, JSON is not a framed protocol so
+ trying to serialize more objects with repeated calls to :func:`dump` and
+ the same *fp* will result in an invalid JSON file.
.. function:: load(fp, cls=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, object_pairs_hook=None, **kw)