diff --git a/requirements-dev.txt b/requirements-dev.txt
index 3b5bce0..be7a0a3 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -3,5 +3,5 @@
 # release of ruff/mypy can otherwise turn a green PR red on untouched code.
 # Tool configuration lives in pyproject.toml.
 
-ruff==0.15.20
+ruff==0.15.21
 mypy==2.1.0