Index: sage/graphs/graph.py
===================================================================
--- sage/graphs/graph.py	(revision 6632)
+++ sage/graphs/graph.py	(revision 6633)
@@ -1972,17 +1972,12 @@
             raise TypeError('Both arguments must be of the same class.')
         if self.is_directed():
-            D = DiGraph()
-            D.add_vertices(self.vertices())
-            D.add_vertices(other.vertices())
-            D.add_edges(self.edges())
-            D.add_edges(other.edges())
-            return D
+            G = DiGraph()
         else:
             G = Graph()
-            G.add_vertices(self.vertices())
-            G.add_vertices(other.vertices())
-            G.add_edges(self.edges())
-            G.add_edges(other.edges())
-            return G
+        G.add_vertices(self.vertices())
+        G.add_vertices(other.vertices())
+        G.add_edges(self.edges())
+        G.add_edges(other.edges())
+        return G
 
     def cartesian_product(self, other):