diff --git a/INSTALL.md b/INSTALL.md
index cdfc743..33629cd 100644
--- a/INSTALL.md
+++ b/INSTALL.md
@@ -10,7 +10,7 @@ What you need on the server:
 | Component | Why |
 |-----------|-----|
 | nginx | serves the static files and passes `*.php` to PHP-FPM |
-| PHP 8.2+ with FPM | the `auth/` backend (login, accounts, admin API) |
+| PHP 8.4 with FPM | the `auth/` backend (login, accounts, admin API). Developed and tested on 8.4 |
 | PHP extensions: `redis`, `mbstring`, `openssl`, `json`, `session` | used by `auth/lib.php` |
 | Redis 6+ | stores accounts, sessions, bans, talkgroup requests |
 | A way to send e-mail | signup verification and password reset (local MTA **or** an SMTP relay, see step 5) |