Issue #17147. Mention BytesIO in SpooledTemporaryFile documentation.
diff --git a/Lib/tempfile.py b/Lib/tempfile.py
index b8fc18c..86300b6 100644
--- a/Lib/tempfile.py
+++ b/Lib/tempfile.py
@@ -479,8 +479,8 @@
             raise
 
 class SpooledTemporaryFile:
-    """Temporary file wrapper, specialized to switch from
-    StringIO to a real file when it exceeds a certain size or
+    """Temporary file wrapper, specialized to switch from BytesIO
+    or StringIO to a real file when it exceeds a certain size or
     when a fileno is needed.
     """
     _rolled = False