diff --git a/libs/ardour/session_events.cc b/libs/ardour/session_events.cc
index 122780894b..a3a7126e99 100644
--- a/libs/ardour/session_events.cc
+++ b/libs/ardour/session_events.cc
@@ -250,15 +250,18 @@ SessionEventManager::_replace_event (SessionEvent* ev)
 	bool ret = false;
 	Events::iterator i;
 
-	/* private, used only for events that can only exist once in the queue */
+	/* use only for events that can only exist once in the respective queue */
+	Events& e (ev->action_sample == SessionEvent::Immediate ? immediate_events : events);
 
-	for (i = events.begin(); i != events.end(); ++i) {
-		if ((*i)->type == ev->type && ev->type == SessionEvent::Overwrite && (*i)->track.lock() == ev->track.lock()) {
+	for (i = e.begin(); i != e.end(); ++i) {
+		if ((*i)->type == ev->type && ev->type == SessionEvent::Overwrite && (*i)->track.lock() == ev->track.lock() && (*i)->overwrite == ev->overwrite) {
+			assert (ev->action_sample == SessionEvent::Immediate);
 			ret = true;
 			delete ev;
 			break;
 		}
 		else if ((*i)->type == ev->type && ev->type != SessionEvent::Overwrite) {
+			assert (ev->action_sample != SessionEvent::Immediate);
 			assert (ev->type == SessionEvent::PunchIn || ev->type == SessionEvent::PunchOut ||  ev->type == SessionEvent::AutoLoop);
 			(*i)->action_sample = ev->action_sample;
 			(*i)->target_sample = ev->target_sample;
@@ -270,12 +273,17 @@ SessionEventManager::_replace_event (SessionEvent* ev)
 		}
 	}
 
-	if (i == events.end()) {
-		events.insert (events.begin(), ev);
+	if (i == e.end()) {
+		e.insert (e.begin(), ev);
 	}
 
-	events.sort (SessionEvent::compare);
-	next_event = events.end();
+	if (ev->action_sample == SessionEvent::Immediate) {
+		/* no need to sort immediate events */
+		return ret;
+	}
+
+	e.sort (SessionEvent::compare);
+	next_event = e.end();
 	set_next_event ();
 
 	return ret;