diff --git a/pyproject.toml b/pyproject.toml
index 013b7db..761bcfc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -43,7 +43,7 @@ mypy = "^1.15.0"
 invoke = "^2.2.0"
 hypothesis = "^6.108"
 tomli = "^2.2.1"
-black = "^24.1.0"
+black = ">=24.1,<26.0"
 isort = "^5.13.2"
 flake8 = "^6.1.0"
 scikit-survival = "^0.24.1"