diff --git a/synapse/config/auth.py b/synapse/config/auth.py
index c7ab428f28af..3b4c77f5727a 100644
--- a/synapse/config/auth.py
+++ b/synapse/config/auth.py
@@ -31,7 +31,7 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
 
         # 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)
         )