diff --git a/src/angst/_core.py b/src/angst/_core.py
index 9f23867..46dabcc 100644
--- a/src/angst/_core.py
+++ b/src/angst/_core.py
@@ -5,6 +5,8 @@
 
 """
 
+from __future__ import annotations
+
 __all__ = [
     "inv_triangle_number",
 ]