diff --git a/src/calibre/srv/render_book.py b/src/calibre/srv/render_book.py
index 01df39b631..6bf6bd3533 100644
--- a/src/calibre/srv/render_book.py
+++ b/src/calibre/srv/render_book.py
@@ -42,7 +42,7 @@ def encode_url(name, frag=''):
 
 def decode_url(x):
     parts = x.split('#', 1)
-    return decode_component(parts[0]), parts[1] if len(parts) > 1 else ''
+    return decode_component(parts[0]), (parts[1] if len(parts) > 1 else '')
 
 class Container(ContainerBase):