diff --git a/libs/ardour/session_vst.cc b/libs/ardour/session_vst.cc
index 20505821bf..805d65450e 100644
--- a/libs/ardour/session_vst.cc
+++ b/libs/ardour/session_vst.cc
@@ -189,12 +189,12 @@ intptr_t Session::vst_callback (
 			timeinfo->sampleRate = session->sample_rate();
 
 			if (value & (kVstTempoValid)) {
-				const Tempo& t (tmap->metric_at (now).tempo());
+				const Tempo& t (tmap->metric_at (timepos_t (now)).tempo());
 				timeinfo->tempo = t.quarter_notes_per_minute ();
 				newflags |= (kVstTempoValid);
 			}
 			if (value & (kVstTimeSigValid)) {
-				const Meter& ms (tmap->metric_at (now).meter());
+				const Meter& ms (tmap->metric_at (timepos_t (now)).meter());
 				timeinfo->timeSigNumerator = ms.divisions_per_bar ();
 				timeinfo->timeSigDenominator = ms.note_value ();
 				newflags |= (kVstTimeSigValid);
diff --git a/libs/ardour/vst3_plugin.cc b/libs/ardour/vst3_plugin.cc
index bb5b719c82..22df1c3569 100644
--- a/libs/ardour/vst3_plugin.cc
+++ b/libs/ardour/vst3_plugin.cc
@@ -653,7 +653,7 @@ VST3Plugin::connect_and_run (BufferSet&  bufs,
 
 	{
 		TempoMap::SharedPtr tmap (TempoMap::use());
-		const TempoMetric&  metric (tmap->metric_at (start));
+		const TempoMetric&  metric (tmap->metric_at (timepos_t (start)));
 		const BBT_Time&     bbt (metric.bbt_at (timepos_t (start)));
 
 		context.tempo              = metric.tempo().quarter_notes_per_minute ();