diff --git a/src/allmydata/storage/http_client.py b/src/allmydata/storage/http_client.py
index fc165bedd..f786b8f30 100644
--- a/src/allmydata/storage/http_client.py
+++ b/src/allmydata/storage/http_client.py
@@ -807,11 +807,10 @@ class StorageClientImmutables(object):
             url,
         )
         if response.code == http.OK:
-            body = cast(
+            return cast(
                 Set[int],
                 await self._client.decode_cbor(response, _SCHEMAS["list_shares"]),
             )
-            return set(body)
         else:
             raise ClientException(response.code)