diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index ab5a043..33cbb7e 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -299,11 +299,11 @@
       Note that it's already possible to iterate on file objects using ``for
       line in file: ...`` without calling ``file.readlines()``.
 
-   .. method:: seek(offset, whence=SEEK_SET)
+   .. method:: seek(offset[, whence])
 
       Change the stream position to the given byte *offset*.  *offset* is
-      interpreted relative to the position indicated by *whence*.  Values for
-      *whence* are:
+      interpreted relative to the position indicated by *whence*.  The default
+      value for *whence* is :data:`SEEK_SET`.  Values for *whence* are:
 
       * :data:`SEEK_SET` or ``0`` -- start of the stream (the default);
         *offset* should be zero or positive
@@ -716,10 +716,11 @@
 
       If *limit* is specified, at most *limit* characters will be read.
 
-   .. method:: seek(offset, whence=SEEK_SET)
+   .. method:: seek(offset[, whence])
 
-      Change the stream position to the given *offset*.  Behaviour depends
-      on the *whence* parameter:
+      Change the stream position to the given *offset*.  Behaviour depends on
+      the *whence* parameter.  The default value for *whence* is
+      :data:`SEEK_SET`.
 
       * :data:`SEEK_SET` or ``0``: seek from the start of the stream
         (the default); *offset* must either be a number returned by
diff --git a/Misc/ACKS b/Misc/ACKS
index 5650f9b..b13fe45 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1257,6 +1257,7 @@
 Pete Shinners
 Michael Shiplett
 John W. Shipman
+Shiyao Ma
 Joel Shprentz
 Yue Shuaijie
 Terrel Shumway
diff --git a/Modules/_io/bytesio.c b/Modules/_io/bytesio.c
index 6498320..f643e91 100644
--- a/Modules/_io/bytesio.c
+++ b/Modules/_io/bytesio.c
@@ -490,7 +490,7 @@
 }
 
 PyDoc_STRVAR(seek_doc,
-"seek(pos, whence=0) -> int.  Change stream position.\n"
+"seek(pos[, whence]) -> int.  Change stream position.\n"
 "\n"
 "Seek to byte offset pos relative to position indicated by whence:\n"
 "     0  Start of stream (the default).  pos should be >= 0;\n"