diff --git a/gtk2_ardour/editor_ops.cc b/gtk2_ardour/editor_ops.cc
index f9018b29c8..4e754dc594 100644
--- a/gtk2_ardour/editor_ops.cc
+++ b/gtk2_ardour/editor_ops.cc
@@ -2248,6 +2248,10 @@ Editor::add_location_from_selection ()
 void
 Editor::add_location_mark (samplepos_t where)
 {
+	if (_session->locations()->mark_at (where, 1)) {
+		return;
+	}
+
 	string markername;
 
 	select_new_marker = true;