diff --git a/joeynmt_server/models/base.py b/joeynmt_server/models/base.py
index 3780ff574e6fd6db187959b5664f0c7e55956232..ceb4c68773f3a7c0e9375496ac91a231ace9ac32 100644
--- a/joeynmt_server/models/base.py
+++ b/joeynmt_server/models/base.py
@@ -38,6 +38,6 @@ class BaseModel(db.Model):
         d = {}
         for key, val in self.sorted_attributes():
             if isinstance(val, dt.datetime):
-                val = val.isoformat()
+                val = val.isoformat(timespec='seconds')
             d[key] = val
         return d
diff --git a/joeynmt_server/views/feedback.py b/joeynmt_server/views/feedback.py
index 0665f2023aed29ee19bbf89b8ea11b669ff048a0..6629052bf69ef71e3d247b66b8d86d7179240eec 100644
--- a/joeynmt_server/views/feedback.py
+++ b/joeynmt_server/views/feedback.py
@@ -107,7 +107,7 @@ def query_feedback():
         model = parse.model if parse else None
         model_lin = parse.lin if parse else None
         joined = {
-            'id': piece.id, 'created': piece.created.isoformat(),
+            'id': piece.id, 'created': piece.created.isoformat(timespec='seconds'),
             'nl': piece.nl, 'correct_lin': piece.correct_lin,
             'original_model': piece.model, 'original_lin': piece.system_lin,
             'parent_id': piece.parent_id,