diff --git a/pyasn1/codec/streaming.py b/pyasn1/codec/streaming.py
index c9ce5f43660a9455c6e56475665e28c6b01c2bd9_cHlhc24xL2NvZGVjL3N0cmVhbWluZy5weQ==..c7a8a8d8f738e8a29b8ef1020e6a79c6192ac890_cHlhc24xL2NvZGVjL3N0cmVhbWluZy5weQ== 100644
--- a/pyasn1/codec/streaming.py
+++ b/pyasn1/codec/streaming.py
@@ -209,7 +209,7 @@
 
     Yields
     ------
-    : :py:class:`bytes` or :py:class:`str` or None
+    : :py:class:`bytes` or :py:class:`str` or :py:class:`SubstrateUnderrunError`
         Returns read data or :py:class:`~pyasn1.error.SubstrateUnderrunError`
         object if no `size` bytes is readily available in the stream. The
         data type depends on Python major version