diff --git a/content/client-server-api/_index.md b/content/client-server-api/_index.md
index bdee69b2..86661422 100644
--- a/content/client-server-api/_index.md
+++ b/content/client-server-api/_index.md
@@ -229,10 +229,6 @@ See the [Server Notices](#server-notices) module for more information.
 `M_THREEPID_MEDIUM_NOT_SUPPORTED`
 The homeserver does not support adding a third party identifier of the given medium.
 
-`M_THREEPID_IN_USE`
-The third party identifier specified by the client is not acceptable because it is
-already in use in some way.
-
 #### Rate limiting
 
 Homeservers SHOULD implement rate limiting to reduce the risk of being