diff --git a/synapse/config/server.py b/synapse/config/server.py
index 8fd231975..cacac253a 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -74,6 +74,9 @@ class ServerConfig(Config):
             self.max_mau_value = config.get(
                 "max_mau_value", 0,
             )
+        self.mau_limits_reserved_threepids = config.get(
+            "mau_limit_reserved_threepid", []
+        )
 
         # FIXME: federation_domain_whitelist needs sytests
         self.federation_domain_whitelist = None