diff --git a/gtk2_ardour/editor.cc b/gtk2_ardour/editor.cc
index f618a057e3..5e7c390e51 100644
--- a/gtk2_ardour/editor.cc
+++ b/gtk2_ardour/editor.cc
@@ -4253,6 +4253,7 @@ Editor::update_grid ()
 		hide_grid_lines ();
 	} else if (grid_musical()) {
 		Temporal::TempoMapPoints grid;
+		grid.reserve (4096);
 		if (bbt_ruler_scale != bbt_show_many) {
 			compute_current_bbt_points (grid, _leftmost_sample, _leftmost_sample + current_page_samples());
 		}
diff --git a/gtk2_ardour/editor_rulers.cc b/gtk2_ardour/editor_rulers.cc
index 2310be8ef8..c74c394b8f 100644
--- a/gtk2_ardour/editor_rulers.cc
+++ b/gtk2_ardour/editor_rulers.cc
@@ -1193,6 +1193,7 @@ Editor::metric_get_bbt (std::vector<ArdourCanvas::Ruler::Mark>& marks, int64_t l
 	const samplecnt_t sr (_session->sample_rate());
 
 	Temporal::TempoMapPoints grid;
+	grid.reserve (4096);
 
 	compute_current_bbt_points (grid, lower, upper);