diff --git a/custom/conf/app.example.ini b/custom/conf/app.example.ini
index 8cd5e6c144..2209822ff0 100644
--- a/custom/conf/app.example.ini
+++ b/custom/conf/app.example.ini
@@ -60,6 +60,7 @@ RUN_USER = ; git
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;
 ;; The protocol the server listens on. One of 'http', 'https', 'http+unix', 'fcgi' or 'fcgi+unix'. Defaults to 'http'
+;; Note: Value must be lowercase.
 ;PROTOCOL = http
 ;;
 ;; Expect PROXY protocol headers on connections
diff --git a/docs/content/administration/config-cheat-sheet.en-us.md b/docs/content/administration/config-cheat-sheet.en-us.md
index ed03bedadb..617715fbaa 100644
--- a/docs/content/administration/config-cheat-sheet.en-us.md
+++ b/docs/content/administration/config-cheat-sheet.en-us.md
@@ -281,6 +281,7 @@ 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**: \[http, https, fcgi, http+unix, fcgi+unix\]
+  - Note: Value must be lowercase.
 - `USE_PROXY_PROTOCOL`: **false**: Expect PROXY protocol headers on connections
 - `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)