diff --git a/libs/ardour/ardour/library.h b/libs/ardour/ardour/library.h
index 5c807d7ec7..8ada7a4b02 100644
--- a/libs/ardour/ardour/library.h
+++ b/libs/ardour/ardour/library.h
@@ -66,6 +66,7 @@ class LIBARDOUR_API LibraryFetcher {
 	int add (std::string const & root_dir);
 
 	int get_descriptions ();
+	size_t n_descriptions() const { return _descriptions.size(); }
 	void foreach_description (boost::function<void (LibraryDescription)> f) const;
 
 	bool installed (LibraryDescription const & desc);