diff --git a/setup.py b/setup.py
index b2e53826e6..a8e1154dc6 100644
--- a/setup.py
+++ b/setup.py
@@ -79,7 +79,9 @@
     license="MIT OR Apache-2.0",
     packages=find_packages(),
     install_requires=[
-        "attrs >= 19.2.0",  # for eq
+        # attrs 19.2.0 adds `eq` option to decorators
+        # attrs 20.1.0 adds @frozen
+        "attrs >= 20.1.0",
         "sortedcontainers",
         "idna",
         "outcome",
diff --git a/test-requirements.in b/test-requirements.in
index 6e94409005..e8c73aed3f 100644
--- a/test-requirements.in
+++ b/test-requirements.in
@@ -25,7 +25,7 @@ typing-extensions; implementation_name == "cpython"
 
 # Trio's own dependencies
 cffi; os_name == "nt"
-attrs >= 19.2.0
+attrs >= 20.1.0
 sortedcontainers
 idna
 outcome