diff --git a/worker.py b/worker.py
index 7344aa0..21214b8 100644
--- a/worker.py
+++ b/worker.py
@@ -93,7 +93,7 @@ def work(server):
 
             sid, sidx, ftag = last_idx
             obuf = StringIO()
-            rdr.out.save(buf, obuf, 'jpeg')
+            rdr.out.save(last_buf, obuf, 'jpeg')
             obuf.seek(0)
             gpu_time = last_evt.time_since(two_evts_ago)
             head = ' '.join([sidx, str(gpu_time), ftag])