diff --git a/gtk2_ardour/editor_mouse.cc b/gtk2_ardour/editor_mouse.cc
index 02ddd7addf..29d7f9a2dc 100644
--- a/gtk2_ardour/editor_mouse.cc
+++ b/gtk2_ardour/editor_mouse.cc
@@ -3060,5 +3060,13 @@ Editor::choose_mapping_drag (ArdourCanvas::Item* item, GdkEvent* event)
 		std::cerr << "TWIST\n";
 		begin_reversible_command (_("tempo mapping: mid-twist"));
 		_drags->set (new MappingTwistDrag (this, item, map, *before, *focus, *after, *before_state, ramped), event);
+	} else if (ramped && focus && after) {
+		/* special case 4: user is manipulating a beat line after the INITIAL tempo marker, so there is no prior marker*/
+		std::cerr << "TWIST ON START\n";
+		begin_reversible_command (_("tempo mapping: mid-twist"));
+		before = focus; /* this is unused in MappingTwistDrag, when ramped is true, but let's not pass in garbage */
+		_drags->set (new MappingTwistDrag (this, item, map, *before, *focus, *after, *before_state, ramped), event);
+	} else {
+		abort_tempo_mapping ();  /* NOTREACHED */
 	}
 }