diff --git a/codes/utils.py b/codes/utils.py
index b5133204c621f0e6c06c00a8a7603f866645979b..8b90e5c904e70c02c2e12cb5ba2a356813380e12 100644
--- a/codes/utils.py
+++ b/codes/utils.py
@@ -63,7 +63,7 @@ def kwant2hk(syst, params={}, coordinate_names="xyz"):
 def builder2tb_model(builder):
     from copy import copy
 
-    builder = copy(bulk_graphene)
+    builder = copy(builder)
 
     tb_model = {}
     sites_list = [*builder.sites()]