diff --git a/network.ts b/network.ts
index 8896ec6..8e56e5f 100644
--- a/network.ts
+++ b/network.ts
@@ -206,7 +206,13 @@ export class Network {
     if (!this.is_multigraph && this.hasEdge(args.from, args.to)) return false;
     // throw { message: ERROR.NOT_MULTIGRAPH };
 
-    if (!this.is_directed) [args.from, args.to] = [args.from, args.to].sort();
+    if (!this.is_directed) {
+      const sorted_vertices = [args.from, args.to].sort();
+      const unsorted_vertices = [args.from, args.to];
+      if (unsorted_vertices[0] !== sorted_vertices[0])
+        args.weight = 1 / args.weight;
+      [args.from, args.to] = sorted_vertices;
+    }
 
     this.edges.set(args.id, new Edge(args));
     return true;