diff --git a/src/allmydata/interfaces.py b/src/allmydata/interfaces.py
index 0312ff0d8..fcd773df0 100644
--- a/src/allmydata/interfaces.py
+++ b/src/allmydata/interfaces.py
@@ -486,7 +486,6 @@ class IFileURI(Interface):
 
 class IMutableFileURI(Interface):
     """I am a URI which represents a mutable filenode."""
-    pass
 class INewDirectoryURI(Interface):
     pass
 class IReadonlyNewDirectoryURI(Interface):