diff --git a/dp3/database/database.py b/dp3/database/database.py
index 35b17302..d6df921c 100644
--- a/dp3/database/database.py
+++ b/dp3/database/database.py
@@ -424,10 +424,13 @@ def insert_datapoints(
         with self._master_buffer_locks[etype]:
             if eid in self._master_buffers[etype]:
                 for attr, push_dps in master_changes["pushes"].items():
-                    if attr in self._master_buffers[etype][eid]["pushes"]:
-                        self._master_buffers[etype][eid]["pushes"][attr].extend(push_dps)
-                    else:
-                        self._master_buffers[etype][eid]["pushes"][attr] = push_dps
+                    if "pushes" not in self._master_buffers[etype][eid]:
+                        self._master_buffers[etype][eid]["pushes"] = {}
+                    if attr not in self._master_buffers[etype][eid]["pushes"]:
+                        self._master_buffers[etype][eid]["pushes"][attr] = []
+                    self._master_buffers[etype][eid]["pushes"][attr].extend(push_dps)
+                if "$set" not in self._master_buffers[etype][eid]:
+                    self._master_buffers[etype][eid]["$set"] = {}
                 self._master_buffers[etype][eid]["$set"].update(master_changes["$set"])
             else:
                 self._master_buffers[etype][eid] = master_changes