diff --git a/pyproject.toml b/pyproject.toml
index cfb79ed..7f4b802 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -25,6 +25,7 @@ dependencies = [
   "pyomo>=5",
   "pandas-indexing>=0.4.0",
   "pycountry",
+  "typing-extensions",
 ]
 dynamic = ["version"]