diff --git a/libs/ardour/ardour/internal_return.h b/libs/ardour/ardour/internal_return.h
index 56fa3cf3ba..1dff465cba 100644
--- a/libs/ardour/ardour/internal_return.h
+++ b/libs/ardour/ardour/internal_return.h
@@ -38,6 +38,7 @@ class InternalReturn : public Return
 	XMLNode& get_state ();
 
 	void run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame, pframes_t nframes, bool);
+	bool configure_io (ChanCount, ChanCount);
 	bool can_support_io_configuration (const ChanCount& in, ChanCount& out) const;
 
 	void add_send (InternalSend *);
diff --git a/libs/ardour/internal_return.cc b/libs/ardour/internal_return.cc
index 568604272b..19f677f368 100644
--- a/libs/ardour/internal_return.cc
+++ b/libs/ardour/internal_return.cc
@@ -89,3 +89,10 @@ InternalReturn::can_support_io_configuration (const ChanCount& in, ChanCount& ou
 	out = in;
 	return true;
 }
+
+bool
+InternalReturn::configure_io (ChanCount in, ChanCount out)
+{
+	IOProcessor::configure_io (in, out);
+	return true;
+}