diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index 1534385d7e..ae109032f4 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -537,10 +537,21 @@ Route::process_output_buffers (BufferSet& bufs,
 			}
 		}
 
-		if (speed < 0) {
-			(*i)->run (bufs, start_sample + latency, end_sample + latency, pspeed, nframes, *i != _processors.back());
-		} else {
-			(*i)->run (bufs, start_sample - latency, end_sample - latency, pspeed, nframes, *i != _processors.back());
+		/* run_disk_reader being false means we are still inside
+		 * latency_preroll, and during this time we do not want to run
+		 * the triggerbox at all. The disk reader looks at the speed
+		 * (pspeed) that was reset to zero as a indication of how it
+		 * should behave. The triggerbox is not speed-sensitive in the
+		 * same way, so we need a more explicit test here to avoid
+		 * running it.
+		 */
+
+		if (run_disk_reader || ((*i) != _triggerbox)) {
+			if (speed < 0) {
+				(*i)->run (bufs, start_sample + latency, end_sample + latency, pspeed, nframes, *i != _processors.back());
+			} else {
+				(*i)->run (bufs, start_sample - latency, end_sample - latency, pspeed, nframes, *i != _processors.back());
+			}
 		}
 
 		bufs.set_count ((*i)->output_streams());