1 files changed, 5 insertions, 4 deletions
diff --git a/synapse/rest/client/v2_alpha/sync.py b/synapse/rest/client/v2_alpha/sync.py
index e321668698..e18f4d01b3 100644
--- a/synapse/rest/client/v2_alpha/sync.py
+++ b/synapse/rest/client/v2_alpha/sync.py
@@ -259,10 +259,11 @@ class SyncRestServlet(RestServlet):
# Corresponding synapse issue: https://github.com/matrix-org/synapse/issues/10456
response["device_one_time_keys_count"] = sync_result.device_one_time_keys_count
- if sync_result.device_unused_fallback_key_types:
- response[
- "org.matrix.msc2732.device_unused_fallback_key_types"
- ] = sync_result.device_unused_fallback_key_types
+ # https://github.com/matrix-org/matrix-doc/blob/54255851f642f84a4f1aaf7bc063eebe3d76752b/proposals/2732-olm-fallback-keys.md
+ # states that this field should always be included, as long as the server supports the feature.
+ response[
+ "org.matrix.msc2732.device_unused_fallback_key_types"
+ ] = sync_result.device_unused_fallback_key_types
if joined:
response["rooms"][Membership.JOIN] = joined
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