diff --git a/changelog.d/9946.misc b/changelog.d/9946.misc
new file mode 100644
index 000000000..142ec5496
--- /dev/null
+++ b/changelog.d/9946.misc
@@ -0,0 +1 @@
+Unpin attrs dependency.
diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index 7709361f1..45a6b8283 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -79,7 +79,7 @@ REQUIREMENTS = [
     # Fedora 31 only has 19.1, so if we want to upgrade we should wait until 33
     # is out in November.)
     # Note: 21.1.0 broke `/sync`, see #9936
-    "attrs>=19.1.0,<21.1.0",
+    "attrs>=19.1.0,!=21.1.0",
     "netaddr>=0.7.18",
     "Jinja2>=2.9",
     "bleach>=1.4.3",