diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index e83fb471c2..b82b9628f8 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -421,10 +421,13 @@ AudioEngine::process_callback (pframes_t nframes)
 	}
 
 	if (!_freewheeling || Freewheel.empty()) {
-		double engine_speed = tmm.pre_process_transport_masters (nframes, sample_time_at_cycle_start());
-		engine_speed = _session->plan_master_strategy (nframes, tmm.get_current_speed_in_process_context(), tmm.get_current_position_in_process_context(), engine_speed);
-		Port::set_speed_ratio (engine_speed);
-		DEBUG_TRACE (DEBUG::Slave, string_compose ("transport master (current=%1) gives speed %2 (ports using %3)\n", tmm.current() ? tmm.current()->name() : string("[]"), engine_speed, Port::speed_ratio()));
+		/* catch_speed is the speed that we estimate we need to run at
+		   to catch (or remain locked to) a transport master.
+		*/
+		double catch_speed = tmm.pre_process_transport_masters (nframes, sample_time_at_cycle_start());
+		catch_speed = _session->plan_master_strategy (nframes, tmm.get_current_speed_in_process_context(), tmm.get_current_position_in_process_context(), catch_speed);
+		Port::set_speed_ratio (catch_speed);
+		DEBUG_TRACE (DEBUG::Slave, string_compose ("transport master (current=%1) gives speed %2 (ports using %3)\n", tmm.current() ? tmm.current()->name() : string("[]"), catch_speed, Port::speed_ratio()));
 
 #if 0 // USE FOR DEBUG ONLY
 		/* use with Dummy backend, engine pulse and