diff --git a/pyproject.toml b/pyproject.toml
index e382f89..8746461 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -59,7 +59,7 @@ pytest-cov = ">=2.4.0"
 pytest-mypy = "==0.10.3"
 mypy = "==1.8.0"
 pycodestyle = "^2.12.1"
-isort = "^5.13.2"
+isort = ">=5.13.2,<9.0.0"
 
 
 [tool.poetry.group.contract-tests]