diff --git a/server.c b/server.c
index 2906fb87..6fdcf940 100644
--- a/server.c
+++ b/server.c
@@ -1377,6 +1377,11 @@ server_lock_server(void)
 		if ((s = ARRAY_ITEM(&sessions, i)) == NULL)
 			continue;
 
+		if (s->flags & SESSION_UNATTACHED) {
+			s->activity = time(NULL);
+			continue;
+		}
+
 		timeout = options_get_number(&s->options, "lock-after-time");
 		if (timeout <= 0 || t <= s->activity + timeout)
 			return;	/* not timed out */
@@ -1400,6 +1405,11 @@ server_lock_sessions(void)
 		if ((s = ARRAY_ITEM(&sessions, i)) == NULL)
 			continue;
 
+		if (s->flags & SESSION_UNATTACHED) {
+			s->activity = time(NULL);
+			continue;
+		}
+
 		timeout = options_get_number(&s->options, "lock-after-time");
 		if (timeout > 0 && t > s->activity + timeout) {
 			server_lock_session(s);