diff -r 4a170261cc54 -r da87dbdf3daf lemon/smart_graph.h
--- a/lemon/smart_graph.h	Thu Feb 25 09:46:12 2021 +0100
+++ b/lemon/smart_graph.h	Tue Jul 28 21:23:36 2020 +0200
@@ -863,7 +863,8 @@
     public:
       RedNode() {}
       RedNode(const RedNode& node) : Node(node) {}
-      RedNode(Invalid) : Node(INVALID){}
+      RedNode(Invalid) : Node(INVALID) {}
+      const RedNode& operator=(const RedNode& node) { Node::operator=(node); return *this;}
     };
 
     class BlueNode : public Node {
@@ -876,6 +877,7 @@
       BlueNode() {}
       BlueNode(const BlueNode& node) : Node(node) {}
       BlueNode(Invalid) : Node(INVALID){}
+      const BlueNode& operator=(const BlueNode& node) { Node::operator=(node); return *this;}
     };
 
     class Edge {