diff --git a/docs/en/00_Getting_Started/03_Environment_Management.md b/docs/en/00_Getting_Started/03_Environment_Management.md
index 4ab96be35..ea8abeedd 100644
--- a/docs/en/00_Getting_Started/03_Environment_Management.md
+++ b/docs/en/00_Getting_Started/03_Environment_Management.md
@@ -122,4 +122,6 @@ Silverstripe core environment variables are listed here, though you're free to d
 | `SS_DATABASE_SSL_CA` | Absolute path to SSL Certificate Authority bundle file |
 | `SS_DATABASE_SSL_CIPHER` | Optional setting for custom SSL cipher |
 | `SS_FLUSH_ON_DEPLOY` | Try to detect deployments through file system modifications and flush on the first request after every deploy. Does not run "dev/build", but only "flush". Possible values are `true` (check for a framework PHP file modification time), `false` (no checks, skip deploy detection) or a path to a specific file or folder to be checked. See [DeployFlushDiscoverer](api:SilverStripe\Core\Startup\DeployFlushDiscoverer) for more details.<br /><br />False by default. |
-| `TEMP_PATH` | Temporary file storage used for the default cache adapters in [Manifests](/developer_guides/execution_pipeline/manifests), [Object Caching](/developer_guides/performance/caching) and [Partial Template Caching](/developer_guides/templates/partial_template_caching). |
+
+Note: A few additional PHP constants can be configured through a custom `index.php` rather than environment variables - see [constants.php](https://github.com/silverstripe/silverstripe-framework/blob/4/src/includes/constants.php) for details.
+Most notably, `TEMP_PATH` can be set as file storage used for the default cache adapters in [Manifests](/developer_guides/execution_pipeline/manifests), [Object Caching](/developer_guides/performance/caching) and [Partial Template Caching](/developer_guides/templates/partial_template_caching). It defaults to PHP's built-in `sys_get_temp_dir()`.