diff --git a/changelog.d/9619.misc b/changelog.d/9619.misc
new file mode 100644
index 0000000000000000000000000000000000000000..50267bfbc472e1bbfb038c2d9bd717ea78a5faff
--- /dev/null
+++ b/changelog.d/9619.misc
@@ -0,0 +1 @@
+Prevent attempting to bundle aggregations for state events in /context APIs.
\ No newline at end of file
diff --git a/synapse/rest/admin/rooms.py b/synapse/rest/admin/rooms.py
index f2c42a0f30a40f158f4621be4814014eb615301d..263d8ec07619a362afcff29fab0dd8d5a0185132 100644
--- a/synapse/rest/admin/rooms.py
+++ b/synapse/rest/admin/rooms.py
@@ -685,7 +685,10 @@ class RoomEventContextServlet(RestServlet):
             results["events_after"], time_now
         )
         results["state"] = await self._event_serializer.serialize_events(
-            results["state"], time_now
+            results["state"],
+            time_now,
+            # No need to bundle aggregations for state events
+            bundle_aggregations=False,
         )
 
         return 200, results
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 9a1df30c2999e32d611063b1e752c769659228ad..5884daea6da22e73f0dd42c933920d81f67548a4 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -671,7 +671,10 @@ class RoomEventContextServlet(RestServlet):
             results["events_after"], time_now
         )
         results["state"] = await self._event_serializer.serialize_events(
-            results["state"], time_now
+            results["state"],
+            time_now,
+            # No need to bundle aggregations for state events
+            bundle_aggregations=False,
         )
 
         return 200, results