diff --git a/src/sparselm/_utils/validation.py b/src/sparselm/_utils/validation.py
index d8d326f..dd697d7 100644
--- a/src/sparselm/_utils/validation.py
+++ b/src/sparselm/_utils/validation.py
@@ -1,5 +1,7 @@
 """Data and hyper-parameters validation utilities."""
 
+from __future__ import annotations
+
 import numpy as np
 from numpy.typing import NDArray
 
diff --git a/src/sparselm/model_selection.py b/src/sparselm/model_selection.py
index fc3ce24..70df8bc 100644
--- a/src/sparselm/model_selection.py
+++ b/src/sparselm/model_selection.py
@@ -1,4 +1,7 @@
 """Classes implementing parameters selection beyond GridsearchCV."""
+
+from __future__ import annotations
+
 __author__ = "Fengyu Xie"
 
 import numbers