diff --git a/lemon/smart_graph.h b/lemon/smart_graph.h
--- a/lemon/smart_graph.h
+++ b/lemon/smart_graph.h
@@ -464,8 +464,8 @@
       explicit Arc(int id) { _id = id;}
 
     public:
-      operator Edge() const { 
-        return _id != -1 ? edgeFromId(_id / 2) : INVALID; 
+      operator Edge() const {
+        return _id != -1 ? edgeFromId(_id / 2) : INVALID;
       }
 
       Arc() {}