diff --git a/gtk2_ardour/ardour_ui.cc b/gtk2_ardour/ardour_ui.cc
index c6634856c9..028c6f29aa 100644
--- a/gtk2_ardour/ardour_ui.cc
+++ b/gtk2_ardour/ardour_ui.cc
@@ -2001,7 +2001,7 @@ ARDOUR_UI::transport_ffwd_rewind (bool fwd)
 	// (keypress auto-repeat is 100ms)
 	const float maxspeed = Config->get_shuttle_max_speed();
 	float semitone_ratio = exp2f (1.0f/12.0f);
-	float octave_down = pow (1.0/semitone_ratio, 12.0);
+	const float octave_down = pow (1.0/semitone_ratio, 12.0);
 	float transport_speed = _session->actual_speed();
 	float speed;