#9957: document that SpooledTemporaryFile.truncate does not take size arg
diff --git a/Doc/library/tempfile.rst b/Doc/library/tempfile.rst
index fff6c4e..c143b88 100644
--- a/Doc/library/tempfile.rst
+++ b/Doc/library/tempfile.rst
@@ -76,7 +76,8 @@
data is spooled in memory until the file size exceeds *max_size*, or
until the file's :func:`fileno` method is called, at which point the
contents are written to disk and operation proceeds as with
- :func:`TemporaryFile`.
+ :func:`TemporaryFile`. Also, it's ``truncate`` method does not
+ accept a ``size`` argument.
The resulting file has one additional method, :func:`rollover`, which
causes the file to roll over to an on-disk file regardless of its size.