diff --git a/borgweb/borg/views/json.py b/borgweb/borg/views/json.py
index ef6aee6..17d7a79 100644
--- a/borgweb/borg/views/json.py
+++ b/borgweb/borg/views/json.py
@@ -10,7 +10,7 @@ def repo_json(request, repo_label):
     repo = get_object_or_404(Repo, label__label=repo_label)
     repo_dict = {'location': repo.location,
                  'latest_backup': "repo.last_backup()",
-                 'size': repo.size_string(),
+                 'size': "repo.size_string()",
                  'recent_errors': "not implemented",
                  'warning': repo.warning(),
                  'error': repo.error()}