diff --git a/superxas_bec/devices/timepix/timepix.py b/superxas_bec/devices/timepix/timepix.py
index 1de20f5..f97d99b 100644
--- a/superxas_bec/devices/timepix/timepix.py
+++ b/superxas_bec/devices/timepix/timepix.py
@@ -469,16 +469,13 @@ class Timepix(PSIDeviceBase, TimePixControl):
         # Register the callback for processing data received by the backend
         # TODO add initial callback again once issues are resolved
         # self.backend.add_callback(self.msg_buffer_callback)
-        self._msg_dump = {}
+        self._msg_dump = []
 
         def _on_msg_received(start_frame, data_frame, end_frame):
             """Callback"""
-            ii = len(self._msg_dump)
-            self._msg_dump[ii] = {
-                "start_frame": start_frame,
-                "data_frame": data_frame,
-                "end_frame": end_frame,
-            }
+            self._msg_dump.append(
+                {"start_frame": start_frame, "data_frame": data_frame, "end_frame": end_frame}
+            )
 
         self.backend.add_callback(_on_msg_received)
 
@@ -676,6 +673,7 @@ if __name__ == "__main__":  # pragma: no cover
             status.wait(timeout=10)
             print("Timepix scan completed.")
             timepix.unstage()
+            timepix._msg_dump.clear()
             print("Timepix unstaged.")
     except Exception as e:
         content = traceback.format_exc()