diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 9fd3539dae..adaa3ccc84 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -6367,6 +6367,7 @@ Session::start_time_changed (framepos_t old)
 	if (l && l->start() == old) {
 		l->set_start (s->start(), true);
 	}
+	set_dirty ();
 }
 
 void
@@ -6386,6 +6387,7 @@ Session::end_time_changed (framepos_t old)
 	if (l && l->end() == old) {
 		l->set_end (s->end(), true);
 	}
+	set_dirty ();
 }
 
 std::vector<std::string>