diff --git a/proposals/2403-knock.md b/proposals/2403-knock.md
index cd89fe23..9972c04c 100644
--- a/proposals/2403-knock.md
+++ b/proposals/2403-knock.md
@@ -75,6 +75,15 @@ The user wasn't allowed to knock (e.g. they are banned). Example error reply:
 }
 ```
 
+##### Status code 404:
+The room was not found. Example error reply:
+```json
+{
+  "errcode": "M_NOT_FOUND",
+  "error": "Unknown room."
+}
+```
+
 ### Extensions to `GET /_matrix/client/r0/sync`
 
 In [the response to
@@ -289,6 +298,15 @@ This request was invalid, e.g. bad JSON. Example reply:
 }
 ```
 
+##### Status code 403:
+This request is forbidden, e.g. the user is banned from the room. Example reply:
+```json
+{
+  "errcode": "M_FORBIDDEN",
+  "error": "You are not allowed to knock on this room"
+}
+```
+
 ##### Status code 404:
 The room is unknown to the remote server. Example reply:
 ```json
@@ -399,6 +417,24 @@ request content.
 }
 ```
 
+##### Status code 403:
+This request is forbidden, e.g. the user is banned from the room. Example reply:
+```json
+{
+  "errcode": "M_FORBIDDEN",
+  "error": "You are not allowed to knock on this room"
+}
+```
+
+##### Status code 404:
+The room is unknown to the remote server. Example reply:
+```json
+{
+  "errcode": "M_NOT_FOUND",
+  "error": "Unknown room"
+}
+```
+
 ## Restrictions
 There are restrictions to being able to set this membership, as well as
 accepting or denying the knock.  A formal description of the changes to the auth rules is given below;