diff --git a/Doc/library/ssl.rst b/Doc/library/ssl.rst
--- a/Doc/library/ssl.rst
+++ b/Doc/library/ssl.rst
@@ -1588,8 +1588,17 @@
 Notes on non-blocking sockets
 -----------------------------
 
-When working with non-blocking sockets, there are several things you need
-to be aware of:
+SSL sockets behave slightly different than regular sockets in
+non-blocking mode. When working with non-blocking sockets, there are
+thus several things you need to be aware of:
+
+- Most :class:`SSLSocket` methods will raise either
+  :exc:`SSLWantWriteError` or :exc:`SSLWantReadError` instead of
+  :exc:`BlockingIOError` if an I/O operation would
+  block. However, **the** :meth:`SSLSocket.send` **method returns zero in
+  this situation** instead of raising any exception (this behavior is
+  mostly a historical accident that has not bene changed for
+  backwards compatibility reasons).
 
 - Calling :func:`~select.select` tells you that the OS-level socket can be
   read from (or written to), but it does not imply that there is sufficient
@@ -1615,7 +1624,8 @@
         except ssl.SSLWantWriteError:
             select.select([], [sock], [])
 
-
+  
+  
 .. _ssl-security:
 
 Security considerations