diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index f72b81d41..a3d7739ea 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -2599,8 +2599,19 @@ class FederationHandler(BaseHandler):
                 original_invite_id, allow_none=True
             )
         if original_invite:
-            display_name = original_invite.content["display_name"]
-            event_dict["content"]["third_party_invite"]["display_name"] = display_name
+            # If the m.room.third_party_invite event's content is empty, it means the
+            # invite has been revoked.
+            if original_invite.content:
+                display_name = original_invite.content["display_name"]
+                event_dict["content"]["third_party_invite"]["display_name"] = display_name
+            else:
+                # Don't discard or raise an error here because that's not the right place
+                # to do auth checks. The auth check will fail on this invite because we
+                # won't be able to fetch public keys from the m.room.third_party_invite
+                # event's content (because it's empty).
+                logger.info(
+                    "Found invite event for third_party_invite but it has been revoked"
+                )
         else:
             logger.info(
                 "Could not find invite event for third_party_invite: %r", event_dict