Index: b/clientloop.c
===================================================================
--- a/clientloop.c
+++ b/clientloop.c
@@ -502,16 +502,21 @@
 static void
 server_alive_check(void)
 {
-	if (packet_inc_alive_timeouts() > options.server_alive_count_max) {
-		logit("Timeout, server not responding.");
-		cleanup_exit(255);
+	if (compat20) {
+		if (packet_inc_alive_timeouts() > options.server_alive_count_max) {
+			logit("Timeout, server not responding.");
+			cleanup_exit(255);
+		}
+		packet_start(SSH2_MSG_GLOBAL_REQUEST);
+		packet_put_cstring("keepalive@openssh.com");
+		packet_put_char(1);     /* boolean: want reply */
+		packet_send();
+		/* Insert an empty placeholder to maintain ordering */
+		client_register_global_confirm(NULL, NULL);
+	} else {
+		packet_send_ignore(0);
+		packet_send();
 	}
-	packet_start(SSH2_MSG_GLOBAL_REQUEST);
-	packet_put_cstring("keepalive@openssh.com");
-	packet_put_char(1);     /* boolean: want reply */
-	packet_send();
-	/* Insert an empty placeholder to maintain ordering */
-	client_register_global_confirm(NULL, NULL);
 }
 
 /*
@@ -572,7 +577,7 @@
 	 * event pending.
 	 */
 
-	if (options.server_alive_interval == 0 || !compat20)
+	if (options.server_alive_interval == 0)
 		tvp = NULL;
 	else {
 		tv.tv_sec = options.server_alive_interval;
Index: b/ssh_config.5
===================================================================
--- a/ssh_config.5
+++ b/ssh_config.5
@@ -935,7 +935,10 @@
 .Cm ServerAliveCountMax
 is left at the default, if the server becomes unresponsive,
 ssh will disconnect after approximately 45 seconds.
-This option applies to protocol version 2 only.
+This option applies to protocol version 2 only; in protocol version
+1 there is no mechanism to request a response from the server to the
+server alive messages, so disconnection is the responsibility of the TCP
+stack.
 .It Cm ServerAliveInterval
 Sets a timeout interval in seconds after which if no data has been received
 from the server,