diff --git a/cds/modules/flows/tasks.py b/cds/modules/flows/tasks.py
index 5ba5d1c3c..53534f672 100644
--- a/cds/modules/flows/tasks.py
+++ b/cds/modules/flows/tasks.py
@@ -705,7 +705,7 @@ def _create_frames(cls, frames, object_, start_time, time_step, **kwargs):
                 media_type="image",
                 context_type="frame",
                 master_id=object_.version_id,
-                timestamp=start_time + (i + 1) * time_step,
+                timestamp=start_time + i * time_step,
             )
             for i, filename in enumerate(frames)
         ]