1 files changed, 5 insertions, 2 deletions
diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py
index 14025cd219..7f812b8209 100644
--- a/synapse/rest/client/v2_alpha/register.py
+++ b/synapse/rest/client/v2_alpha/register.py
@@ -416,8 +416,11 @@ class RegisterRestServlet(RestServlet):
             )
             # Necessary due to auth checks prior to the threepid being
             # written to the db
-            if is_threepid_reserved(self.hs.config, threepid):
-                yield self.store.upsert_monthly_active_user(registered_user_id)
+            if threepid:
+                if is_threepid_reserved(
+                    self.hs.config.mau_limits_reserved_threepids, threepid
+                ):
+                    yield self.store.upsert_monthly_active_user(registered_user_id)
 
             # remember that we've now registered that user account, and with
             #  what user ID (since the user may not have specified)