diff --git a/setup.py b/setup.py
--- a/setup.py
+++ b/setup.py
@@ -63,7 +63,7 @@ requirements = [
     "Routes >= 2.0, < 2.5",
     "dulwich >= 0.19.0, < 0.20",
     "mercurial >= 5.1, < 5.3",
-    "decorator >= 3.3.2, < 4.5",
+    "decorator >= 4.2.1, < 4.5",
     "Paste >= 2.0.3, < 3.1",
     "bleach >= 3.0, < 3.2",
     "Click >= 7.0, < 8",