Fix running with an empty experimental features section. (#15925)

2 files changed, 2 insertions, 1 deletions

diff --git a/changelog.d/15925.bugfix b/changelog.d/15925.bugfix
new file mode 100644

index 0000000000..e3ef783576
--- /dev/null
+++ b/changelog.d/15925.bugfix
@@ -0,0 +1 @@
+Fix a bug introduced in 1.86.0 where Synapse starting with an empty `experimental_features` configuration setting.
diff --git a/synapse/config/auth.py b/synapse/config/auth.py

index c7ab428f28..3b4c77f572 100644
--- a/synapse/config/auth.py
+++ b/synapse/config/auth.py
@@ -31,7 +31,7 @@ class AuthConfig(Config):
 
         # The default value of password_config.enabled is True, unless msc3861 is enabled.
         msc3861_enabled = (
-            config.get("experimental_features", {})
+            (config.get("experimental_features") or {})
             .get("msc3861", {})
             .get("enabled", False)
         )