diff --git a/src/sage/graphs/spanning_tree.pyx b/src/sage/graphs/spanning_tree.pyx
index 6236bcf1f80..912e016b1e0 100644
--- a/src/sage/graphs/spanning_tree.pyx
+++ b/src/sage/graphs/spanning_tree.pyx
@@ -574,8 +574,7 @@ def filter_kruskal_iterator(G, threshold=10000, by_weight=True, weight_function=
             yield from G.edge_iterator()
             return
 
-        # g = G.to_simple(to_undirected=False, keep_label='min')
-        g = G
+        g = G.to_simple(to_undirected=False, keep_label='min')
     else:
         g = G