diff --git a/synapse/handlers/e2e_room_keys.py b/synapse/handlers/e2e_room_keys.py
index 33d71a172a..f4a531f0c2 100644
--- a/synapse/handlers/e2e_room_keys.py
+++ b/synapse/handlers/e2e_room_keys.py
@@ -101,13 +101,25 @@ class E2eRoomKeysHandler(object):
             session_id(string): session ID to delete keys for, for None to delete keys
                 for all sessions
         Returns:
-            A deferred of the deletion transaction
+            A dict containing the count and hash for the backup version
         """
 
         # lock for consistency with uploading
         with (yield self._upload_linearizer.queue(user_id)):
+            # make sure the backup version exists
+            try:
+                version_info = yield self.store.get_e2e_room_keys_version_info(user_id, version)
+            except StoreError as e:
+                if e.code == 404:
+                    raise NotFoundError("Unknown backup version")
+                else:
+                    raise
+
             yield self.store.delete_e2e_room_keys(user_id, version, room_id, session_id)
 
+            count = yield self.store.count_e2e_room_keys(user_id, version)
+            return {"count": count, "hash": version_info["hash"]}
+
     @defer.inlineCallbacks
     def upload_room_keys(self, user_id, version, room_keys):
         """Bulk upload a list of room keys into a given backup version, asserting
@@ -134,6 +146,9 @@ class E2eRoomKeysHandler(object):
             }
         }
 
+        Returns:
+            A dict containing the count and hash for the backup version
+
         Raises:
             NotFoundError: if there are no versions defined
             RoomKeysVersionError: if the uploaded version is not the current version
diff --git a/synapse/rest/client/v2_alpha/room_keys.py b/synapse/rest/client/v2_alpha/room_keys.py
index 3b7252fb7e..7fb91393b5 100644
--- a/synapse/rest/client/v2_alpha/room_keys.py
+++ b/synapse/rest/client/v2_alpha/room_keys.py
@@ -239,10 +239,10 @@ class RoomKeysServlet(RestServlet):
         user_id = requester.user.to_string()
         version = parse_string(request, "version")
 
-        yield self.e2e_room_keys_handler.delete_room_keys(
+        ret = yield self.e2e_room_keys_handler.delete_room_keys(
             user_id, version, room_id, session_id
         )
-        return (200, {})
+        return (200, ret)
 
 
 class RoomKeysNewVersionServlet(RestServlet):