diff --git a/src/nmreval/models/transitions.py b/src/nmreval/models/transitions.py
index ed80f59..1b25958 100644
--- a/src/nmreval/models/transitions.py
+++ b/src/nmreval/models/transitions.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import numpy as np
 from scipy import special as special