diff --git a/cate/ds/local.py b/cate/ds/local.py
index f9c48a60c..36ea139e4 100644
--- a/cate/ds/local.py
+++ b/cate/ds/local.py
@@ -257,3 +257,4 @@ def _json_default_serializer(obj):
         if isinstance(obj, datetime):
             return obj.replace(microsecond=0).isoformat()
         raise TypeError('Not sure how to serialize %s' % (obj,))
+