diff --git a/pyproject.toml b/pyproject.toml
index 79377c3..aa5149d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,6 +45,9 @@ ignore = ["D", "E501", "ANN401", "BLE001", "COM812", "S101", "PT"]
 [tool.ty.src]
 include = ["cool_domain", "tests"]
 
+[tool.ty.environment]
+python = "./.venv/bin/python3"
+
 [tool.coverage.run]
 source = ["cool_domain"]
 omit = ["cool_domain/logs.py", "cool_domain/__main__.py"]