diff --git a/ruff.toml b/ruff.toml
index 49dd7a8c17..701055a65a 100644
--- a/ruff.toml
+++ b/ruff.toml
@@ -34,6 +34,9 @@ exclude = [
 line-length = 79
 indent-width = 4
 
+# Assume Python 3.9
+target-version = "py39"
+
 [lint]
 preview = true
 pydocstyle.convention = "google"