diff --git a/Misc/NEWS b/Misc/NEWS
index 7a4ac3fba4c..db9b8817fc8 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -96,6 +96,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #8240: Set the SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER flag on SSL
+  sockets.
+
 - Issue #17269: Workaround for socket.getaddrinfo crash on MacOS X
   with port None or "0" and flags AI_NUMERICSERV.
 
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index c6493ba833f..ca41bbfc691 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -490,9 +490,11 @@ newPySSLSocket(PySSLContext *sslctx, PySocketSockObject *sock,
     PySSL_END_ALLOW_THREADS
     SSL_set_app_data(self->ssl,self);
     SSL_set_fd(self->ssl, sock->sock_fd);
+    SSL_set_mode(self->ssl, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER
 #ifdef SSL_MODE_AUTO_RETRY
-    SSL_set_mode(self->ssl, SSL_MODE_AUTO_RETRY);
+                 | SSL_MODE_AUTO_RETRY
 #endif
+                 );
 
 #if HAVE_SNI
     if (server_hostname != NULL)