diff --git a/gtk2_ardour/editor.h b/gtk2_ardour/editor.h
index 610a995c14..2e6f6cac08 100644
--- a/gtk2_ardour/editor.h
+++ b/gtk2_ardour/editor.h
@@ -1755,7 +1755,8 @@ private:
 	enum MidTempoChanges {
 		TempoChanged = 0x1,
 		MeterChanged = 0x2,
-		BBTChanged   = 0x4
+		BBTChanged   = 0x4,
+		MappingChanged = 0x8
 	};
 
 	void mid_tempo_change (MidTempoChanges);
diff --git a/gtk2_ardour/editor_tempodisplay.cc b/gtk2_ardour/editor_tempodisplay.cc
index 996d837a52..124307d902 100644
--- a/gtk2_ardour/editor_tempodisplay.cc
+++ b/gtk2_ardour/editor_tempodisplay.cc
@@ -821,7 +821,7 @@ Editor::mid_tempo_change (MidTempoChanges what_changed)
 	// TempoMap::SharedPtr map (TempoMap::use());
 	// map->dump (std::cerr);
 
-	if ((what_changed & MidTempoChanges(BBTChanged|TempoChanged))) {
+	if ((what_changed & MidTempoChanges(BBTChanged|TempoChanged|MappingChanged))) {
 		double min_tempo = DBL_MAX;
 		double max_tempo = 0.0;