diff --git a/libs/ardour/route.cc b/libs/ardour/route.cc
index 4b4e450c34..a793ae5b2a 100644
--- a/libs/ardour/route.cc
+++ b/libs/ardour/route.cc
@@ -1896,6 +1896,14 @@ Route::configure_processors_unlocked (ProcessorStreams* err)
 		(*p)->configure_io(c->first, c->second);
 		processor_max_streams = ChanCount::max(processor_max_streams, c->first);
 		processor_max_streams = ChanCount::max(processor_max_streams, c->second);
+
+		boost::shared_ptr<PluginInsert> pi;
+		if ((pi = boost::dynamic_pointer_cast<PluginInsert>(*p)) != 0) {
+			/* plugins connected via Split Match may have more channels.
+			 * route/scratch buffers are needed for all of them*/
+			processor_max_streams = ChanCount::max(processor_max_streams, pi->input_streams());
+			processor_max_streams = ChanCount::max(processor_max_streams, pi->natural_input_streams());
+		}
 		out = c->second;
 
 		if (boost::dynamic_pointer_cast<Delivery> (*p)