diff --git a/src/_zkapauthorizer/_storage_server.py b/src/_zkapauthorizer/_storage_server.py
index 0a5a58b344eedbf0fdf25260927e2720c7a60a00..809b385118b2a2f27c32e623c5d97bea2b8fc3be 100644
--- a/src/_zkapauthorizer/_storage_server.py
+++ b/src/_zkapauthorizer/_storage_server.py
@@ -829,6 +829,8 @@ def get_stat(sharepath):
     with open(sharepath, "rb") as share_file:
         magic = share_file.read(32)
         if len(magic) < 32:
+            # Tahoe could check for this.
+            # https://tahoe-lafs.org/trac/tahoe-lafs/ticket/3853
             raise ValueError("Share file has short header")
         if ShareFile.is_valid_header(magic):
             return stat_bucket