diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index b273a4bee..e7a1bb724 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -331,7 +331,7 @@ class AuthHandler(BaseHandler):
 
         identity_handler = self.hs.get_handlers().identity_handler
 
-        logger.info("Getting validated threepid. threepidcreds: %r" % (threepid_creds,))
+        logger.info("Getting validated threepid. threepidcreds: %r", (threepid_creds,))
         threepid = yield identity_handler.threepid_from_creds(threepid_creds)
 
         if not threepid: