diff --git a/gtk2_ardour/rc_option_editor.cc b/gtk2_ardour/rc_option_editor.cc
index 358ff6e107..a57764e9b6 100644
--- a/gtk2_ardour/rc_option_editor.cc
+++ b/gtk2_ardour/rc_option_editor.cc
@@ -1498,13 +1498,21 @@ RCOptionEditor::RCOptionEditor ()
 
 	_sync_genlock = new BoolOption (
 		"timecode-source-is-synced",
-		_("External timecode is sync locked"),
+		_("Sync lock timecode to clock - Disable drift compensation."),
 		sigc::mem_fun (*_rc_config, &RCConfiguration::get_timecode_source_is_synced),
 		sigc::mem_fun (*_rc_config, &RCConfiguration::set_timecode_source_is_synced)
 		);
 	Gtkmm2ext::UI::instance()->set_tip 
-		(_sync_genlock->tip_widget(), 
-		 _("<b>When enabled</b> indicates that the selected external timecode source shares sync (Black &amp; Burst, Wordclock, etc) with the audio interface."));
+		(_sync_genlock->tip_widget(),
+		 string_compose (_("<b>When enabled</b> %1 will never varispeed when slaved to external timecode. "
+				   "Sync Lock indicates that the selected external timecode source shares clock-sync "
+				   "(Black &amp; Burst, Wordclock, etc) with the audio interface. "
+				   "This option disables drift compensation. The transport speed is fixed at 1.0."
+				   "Varispeed LTC will be ignored and cause drift."
+				   "\n\n"
+				   "<b>When disabled</b> %1 will compensate for potential drift, regardless if the "
+				   "timecode sources shares clock sync."
+				  ), PROGRAM_NAME));
 
 
 	add_option (_("Transport"), _sync_genlock);
diff --git a/libs/ardour/ardour/rc_configuration_vars.h b/libs/ardour/ardour/rc_configuration_vars.h
index 1c5f9a82b8..205928cd86 100644
--- a/libs/ardour/ardour/rc_configuration_vars.h
+++ b/libs/ardour/ardour/rc_configuration_vars.h
@@ -50,7 +50,7 @@ CONFIG_VARIABLE (int32_t, inter_scene_gap_msecs, "inter-scene-gap-msecs", 1)
 
 CONFIG_VARIABLE (int, mtc_qf_speed_tolerance, "mtc-qf-speed-tolerance", 5)
 CONFIG_VARIABLE (bool, timecode_sync_frame_rate, "timecode-sync-frame-rate", true)
-CONFIG_VARIABLE (bool, timecode_source_is_synced, "timecode-source-is-synced", true)
+CONFIG_VARIABLE (bool, timecode_source_is_synced, "timecode-source-is-synced", false)
 CONFIG_VARIABLE (bool, timecode_source_2997, "timecode-source-2997", false)
 CONFIG_VARIABLE (SyncSource, sync_source, "sync-source", Engine)
 CONFIG_VARIABLE (std::string, ltc_source_port, "ltc-source-port", "system:capture_1")