diff --git a/src/qibo/hamiltonians/__init__.py b/src/qibo/hamiltonians/__init__.py
index 9826e01833..ce21da1582 100644
--- a/src/qibo/hamiltonians/__init__.py
+++ b/src/qibo/hamiltonians/__init__.py
@@ -1,2 +1,2 @@
 from qibo.hamiltonians.hamiltonians import *
-from qibo.hamiltonians.models import Heisenberg, TFIM, XXZ, MaxCut, X, Y, Z
+from qibo.hamiltonians.models import TFIM, XXZ, Heisenberg, MaxCut, X, Y, Z
diff --git a/src/qibo/hamiltonians/models.py b/src/qibo/hamiltonians/models.py
index 8524591f85..8077eb0520 100644
--- a/src/qibo/hamiltonians/models.py
+++ b/src/qibo/hamiltonians/models.py
@@ -1,6 +1,5 @@
-from typing import Union, List, Tuple
-
 from functools import reduce
+from typing import List, Tuple, Union
 
 import numpy as np