diff --git a/python/pyproject.toml b/python/pyproject.toml
index 23a7342..64d9cfa 100644
--- a/python/pyproject.toml
+++ b/python/pyproject.toml
@@ -17,7 +17,7 @@ dependencies = [
   "numpy>=1.15.4",
   "matplotlib>=2.0.0",
   "pandas>=1.0.4",
-  "holidays>=0.25",
+  "holidays>=0.25,<1",
   "tqdm>=4.36.1",
   "importlib_resources",
 ]