diff --git a/python/polycube_encoder.py b/python/polycube_encoder.py
index ef390ef..d4f24e5 100644
--- a/python/polycube_encoder.py
+++ b/python/polycube_encoder.py
@@ -6,4 +6,6 @@ class PolyCubeEncdoder(JSONEncoder):
     def default(self, o: Any) -> Any:
         if isinstance(o, PolyCube):
             return list(o.cubes)
+        elif isinstance(o, set):
+            return list(o)
         return super().default(o)