diff --git a/setup.py b/setup.py
index 9408427..bb97efd 100644
--- a/setup.py
+++ b/setup.py
@@ -21,7 +21,7 @@
 
 install_requires = [
     "lxml~=4.9.1",
-    "attrs==21.2.*",
+    "attrs>=21.2,<24",
     "sortedcontainers==2.4.*",
     "toposort==1.7",
     "more-itertools==8.12.*",