diff --git a/src/graph_impl/stable_graph/mod.rs b/src/graph_impl/stable_graph/mod.rs
index a3a2dfb..b9a54c9 100644
--- a/src/graph_impl/stable_graph/mod.rs
+++ b/src/graph_impl/stable_graph/mod.rs
@@ -734,6 +734,8 @@
         self.g.raw_nodes()
     }
 
+    // used by check_free_lists conditionally
+    #[allow(unused)]
     fn raw_edges(&self) -> &[Edge<Option<E>, Ix>] {
         self.g.raw_edges()
     }