diff --git a/pyproject.toml b/pyproject.toml
index 7edef29..580af7b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -35,7 +35,7 @@ Repository = "https://github.com/fellowapp/mudder-py"
 Changelog = "https://github.com/fellowapp/mudder-py/releases"
 
 [dependency-groups]
-dev = ["pyright>=1.1.396", "pytest~=8.1", "ruff~=0.4"]
+dev = ["pyright>=1.1.396", "pytest>=8.1,<10.0", "ruff~=0.4"]
 
 [tool.setuptools_scm]