diff --git a/data/api/client-server/registration.yaml b/data/api/client-server/registration.yaml
index 9fe4d4ad..e2100a1a 100644
--- a/data/api/client-server/registration.yaml
+++ b/data/api/client-server/registration.yaml
@@ -51,7 +51,7 @@ paths:
         `username` provided, if any. Note that the grammar of Matrix User ID
         localparts is restricted, so the server MUST either map the provided
         `username` onto a `user_id` in a logical manner, or reject
-        `username`\s which do not comply to the grammar, with
+        `username`s which do not comply to the grammar, with
         `M_INVALID_USERNAME`.
 
         Matrix clients MUST NOT assume that localpart of the registered