diff --git a/src/allmydata/web/operations.py b/src/allmydata/web/operations.py
index 8f78d8a0b..29533523b 100644
--- a/src/allmydata/web/operations.py
+++ b/src/allmydata/web/operations.py
@@ -152,7 +152,7 @@ class ReloadMixin(object):
     @renderer
     def refresh(self, req, tag):
         if self.monitor.is_finished():
-            return b""
+            return ""
         tag.attributes["http-equiv"] = "refresh"
         tag.attributes["content"] = str(self.REFRESH_TIME)
         return tag