#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 6c84f94..546a09d 100644
--- a/Doc/library/json.rst
+++ b/Doc/library/json.rst
@@ -156,6 +156,11 @@
:meth:`default` method to serialize additional types), specify it with the
*cls* kwarg; otherwise :class:`JSONEncoder` is used.
+ .. 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:: dumps(obj[, skipkeys[, ensure_ascii[, check_circular[, allow_nan[, cls[, indent[, separators[, encoding[, default[, **kw]]]]]]]]]])