diff --git a/docs/admin/config-cheat-sheet.md b/docs/admin/config-cheat-sheet.md
index b771e77f..678bbc80 100644
--- a/docs/admin/config-cheat-sheet.md
+++ b/docs/admin/config-cheat-sheet.md
@@ -269,7 +269,7 @@ The following configuration set `Content-Type: application/vnd.android.package-a
 
 - `APP_DATA_PATH`: **_`AppWorkPath`_/data**: This is the default root path for storing data.
 - `PROTOCOL`: **http**: \[http, https, fcgi, http+unix, fcgi+unix\]
-- `USE_PROXY_PROTOCOL`: **false**: Expect PROXY protocol headers on connections
+- `USE_PROXY_PROTOCOL`: **false**: Expect PROXY protocol headers on connections. Warning: this feature is [not working](https://codeberg.org/forgejo/forgejo/issues/633).
 - `PROXY_PROTOCOL_TLS_BRIDGING`: **false**: When protocol is https, expect PROXY protocol headers after TLS negotiation.
 - `PROXY_PROTOCOL_HEADER_TIMEOUT`: **5s**: Timeout to wait for PROXY protocol header (set to 0 to have no timeout)
 - `PROXY_PROTOCOL_ACCEPT_UNKNOWN`: **false**: Accept PROXY protocol headers with Unknown type.