diff --git a/src/allmydata/storage/immutable.py b/src/allmydata/storage/immutable.py
index d17f69c07..0949929a9 100644
--- a/src/allmydata/storage/immutable.py
+++ b/src/allmydata/storage/immutable.py
@@ -384,7 +384,7 @@ class BucketWriter(object):
         start = self._clock.seconds()
         precondition(not self.closed)
         if self.throw_out_all_data:
-            return
+            return False
 
         # Make sure we're not conflicting with existing data:
         end = offset + len(data)