diff --git a/lemon/smart_graph.h b/lemon/smart_graph.h
--- a/lemon/smart_graph.h
+++ b/lemon/smart_graph.h
@@ -508,7 +508,7 @@
       node._id = nodes.size() - 1;
     }
 
-    void next(Node& node) const {
+    static void next(Node& node) {
       --node._id;
     }
 
@@ -516,7 +516,7 @@
       arc._id = arcs.size() - 1;
     }
 
-    void next(Arc& arc) const {
+    static void next(Arc& arc) {
       --arc._id;
     }
 
@@ -524,7 +524,7 @@
       arc._id = arcs.size() / 2 - 1;
     }
 
-    void next(Edge& arc) const {
+    static void next(Edge& arc) {
       --arc._id;
     }