From 46f8ef1c75de61e0fea01c6c88bc33e117facd70 Mon Sep 17 00:00:00 2001
From: Patrick Cloke <patrickc@matrix.org>
Date: Thu, 20 Aug 2020 07:17:29 -0400
Subject: [PATCH] Improve the error code when trying to register using a name
 reserved for guests.

---
 changelog.d/8135.bugfix      | 1 +
 synapse/handlers/register.py | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)
 create mode 100644 changelog.d/8135.bugfix

diff --git a/changelog.d/8135.bugfix b/changelog.d/8135.bugfix
new file mode 100644
index 000000000000..9d5c60ea00e3
--- /dev/null
+++ b/changelog.d/8135.bugfix
@@ -0,0 +1 @@
+Clarify the error code if a user tries to register with a numeric ID. This bug was introduced in v1.15.0.
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index 999bc6efb56a..ccd96e46267a 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -124,7 +124,9 @@ async def check_username(
             try:
                 int(localpart)
                 raise SynapseError(
-                    400, "Numeric user IDs are reserved for guest users."
+                    400,
+                    "Numeric user IDs are reserved for guest users.",
+                    errcode=Codes.INVALID_USERNAME,
                 )
             except ValueError:
                 pass