diff --git a/acme/setup.py b/acme/setup.py
index a8375150d..a6551a023 100644
--- a/acme/setup.py
+++ b/acme/setup.py
@@ -17,7 +17,7 @@ install_requires = [
     'pyrfc3339',
     'pytz',
     'requests',
-    'setuptools==18.5',  # pkg_resources
+    'setuptools',  # pkg_resources
     'six',
     'werkzeug',
 ]