1 files changed, 1 insertions, 1 deletions
diff --git a/synapse/types.py b/synapse/types.py
index 9d64e8c4de..1694af1250 100644
--- a/synapse/types.py
+++ b/synapse/types.py
@@ -56,7 +56,7 @@ def get_domain_from_id(string):
     try:
         return string.split(":", 1)[1]
     except IndexError:
-        raise SynapseError(400, "Invalid ID: %r", string)
+        raise SynapseError(400, "Invalid ID: %r" % (string,))
 
 
 class DomainSpecificString(