diff --git a/Doc/library/ssl.rst b/Doc/library/ssl.rst
index 3cd9554..9b3306c 100644
--- a/Doc/library/ssl.rst
+++ b/Doc/library/ssl.rst
@@ -445,6 +445,14 @@
 
    .. versionadded:: 3.3
 
+.. data:: HAS_ECDH
+
+   Whether the OpenSSL library has built-in support for Elliptic Curve-based
+   Diffie-Hellman key exchange.  This should be true unless the feature was
+   explicitly disabled by the distributor.
+
+   .. versionadded:: 3.3
+
 .. data:: HAS_SNI
 
    Whether the OpenSSL library has built-in support for the *Server Name
@@ -711,6 +719,8 @@
    This setting doesn't apply to client sockets.  You can also use the
    :data:`OP_SINGLE_ECDH_USE` option to further improve security.
 
+   This method is not available if :data:`HAS_ECDH` is False.
+
    .. versionadded:: 3.3
 
    .. seealso::