diff --git a/disco/types/base.py b/disco/types/base.py
index c3a061b..4c0d916 100644
--- a/disco/types/base.py
+++ b/disco/types/base.py
@@ -25,6 +25,9 @@ class Unset(object):
     def __nonzero__(self):
         return False
 
+    def __bool__(self):
+        return False
+
 
 UNSET = Unset()