diff --git a/libs/ardour/midi_track.cc b/libs/ardour/midi_track.cc
index c7768c7249..90b866ca92 100644
--- a/libs/ardour/midi_track.cc
+++ b/libs/ardour/midi_track.cc
@@ -353,7 +353,7 @@ MidiTrack::roll (pframes_t nframes, framepos_t start_frame, framepos_t end_frame
 		return dret;
 	}
 
-	BufferSet& bufs = _session.get_scratch_buffers (n_process_buffers());
+	BufferSet& bufs = _session.get_route_buffers (n_process_buffers());
 
 	fill_buffers_with_input (bufs, _input, nframes);
 
diff --git a/libs/ardour/process_thread.cc b/libs/ardour/process_thread.cc
index 4c9789f37a..5d8d6f34fd 100644
--- a/libs/ardour/process_thread.cc
+++ b/libs/ardour/process_thread.cc
@@ -126,7 +126,7 @@ ProcessThread::get_route_buffers (ChanCount count, bool silence)
 
 	if (silence) {
 		for (DataType::iterator t = DataType::begin(); t != DataType::end(); ++t) {
-			for (size_t i= 0; i < count.get(*t); ++i) {
+			for (uint32_t i = 0; i < sb->count().get(*t); ++i) {
 				sb->get(*t, i).clear();
 			}
 		}