diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 403220f029..8360596e91 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -414,7 +414,7 @@ public:
 
 	void maybe_write_autosave ();
 
-	PBD::Signal0<void> SurroundObjectCountChanged;
+	PBD::Signal1<void, int> SurroundObjectCountChanged;
 
 	/* Emitted when all i/o connections are complete */