diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
index 05b800fead..0a44829bd2 100644
--- a/libs/ardour/session_process.cc
+++ b/libs/ardour/session_process.cc
@@ -349,6 +349,7 @@ Session::process_with_events (pframes_t nframes)
 	}
 
 	end_frame = _transport_frame + frames_moved;
+	_transport_frame = std::max((ARDOUR::framepos_t) 0, _transport_frame);
 
 	{
 		SessionEvent* this_event;
diff --git a/libs/ardour/session_transport.cc b/libs/ardour/session_transport.cc
index 037ca83484..693074cf9a 100644
--- a/libs/ardour/session_transport.cc
+++ b/libs/ardour/session_transport.cc
@@ -851,6 +851,7 @@ Session::micro_locate (framecnt_t distance)
 	}
 
 	_transport_frame += distance;
+	_transport_frame = std::max((ARDOUR::framepos_t) 0, _transport_frame);
 	return 0;
 }
 
@@ -896,6 +897,7 @@ Session::locate (framepos_t target_frame, bool with_roll, bool with_flush, bool
 
 	// Update Timecode time
 	// [DR] FIXME: find out exactly where this should go below
+	target_frame = std::max((ARDOUR::framepos_t) 0, target_frame);
 	_transport_frame = target_frame;
 	_last_roll_or_reversal_location = target_frame;
 	timecode_time(_transport_frame, transmitting_timecode_time);