diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index 73b3efff0f49a5..28aac923cc375b 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -790,7 +790,7 @@ Text I/O
 
       .. versionadded:: 3.1
 
-   .. method:: read(size)
+   .. method:: read(size=-1)
 
       Read and return at most *size* characters from the stream as a single
       :class:`str`.  If *size* is negative or ``None``, reads until EOF.