diff --git a/src/allmydata/grid_manager.py b/src/allmydata/grid_manager.py
index a17a1fab5..319d87002 100644
--- a/src/allmydata/grid_manager.py
+++ b/src/allmydata/grid_manager.py
@@ -69,7 +69,7 @@ class _GridManagerStorageServer(object):
 
     name : str
     public_key : ed25519.Ed25519PublicKey
-    certificates : list = Factory(list)
+    certificates : list = Factory(list)  # SignedCertificates
 
     def add_certificate(self, certificate):
         """