diff --git a/python/polycube.py b/python/polycube.py
index 7b3109b..8c6a9ac 100644
--- a/python/polycube.py
+++ b/python/polycube.py
@@ -27,7 +27,7 @@ class PolyCube:
         for last_addition in self.last_additions:
             growth_candidates = growth_candidates.union(generate_neighbors(*last_addition))
         growth_candidates = growth_candidates.difference(self.cubes)
-        realizable_growth =  chain(combinations(growth_candidates, i) for i in range(1, max_growth+1))
+        realizable_growth =  chain.from_iterable(combinations(growth_candidates, i) for i in range(1, max_growth+1))
         for addition in realizable_growth:
             yield PolyCube(self.cubes.union(addition), addition)