diff --git a/src/applications/config/option/PhabricatorCoreConfigOptions.php b/src/applications/config/option/PhabricatorCoreConfigOptions.php
--- a/src/applications/config/option/PhabricatorCoreConfigOptions.php
+++ b/src/applications/config/option/PhabricatorCoreConfigOptions.php
@@ -36,8 +36,6 @@
       'User Guide: Prototype Applications');
     $proto_doc_name = pht('User Guide: Prototype Applications');
     $applications_app_href = '/applications/';
-    $custom_header_example =
-      PhabricatorCustomHeaderConfigType::getExampleConfig();
 
     return array(
       $this->newOption('phabricator.base-uri', 'string', null)
@@ -211,27 +209,6 @@
         ->setLocked(true)
         ->setDescription(
           pht('Custom HTML to show on the main Phabricator dashboard.')),
-      $this->newOption(
-        'ui.custom-header',
-        'custom:PhabricatorCustomHeaderConfigType',
-        null)
-        ->setSummary(
-          pht('Customize the Phabricator logo.'))
-        ->setDescription(
-          pht('You can customize the Phabricator logo by specifying the '.
-              'phid for a viewable image you have uploaded to Phabricator '.
-              'via the [[ /file/ | Files application]]. This image should '.
-              'be:'."\n".
-              ' - 192px X 80px; while not enforced, images with these '.
-              'dimensions will look best across devices.'."\n".
-              ' - have view policy public if [[ '.
-              '/config/edit/policy.allow-public | `policy.allow-public`]] '.
-              'is true and otherwise view policy user; mismatches in these '.
-              'policy settings will result in a broken logo for some users.'.
-              "\n\n".
-              'You should restart your webserver after updating this value '.
-              'to see this change take effect.'))
-        ->addExample($custom_header_example, pht('Valid Config')),
       $this->newOption('phabricator.cache-namespace', 'string', null)
         ->setLocked(true)
         ->setDescription(pht('Cache namespace.')),
diff --git a/src/applications/config/option/PhabricatorUIConfigOptions.php b/src/applications/config/option/PhabricatorUIConfigOptions.php
--- a/src/applications/config/option/PhabricatorUIConfigOptions.php
+++ b/src/applications/config/option/PhabricatorUIConfigOptions.php
@@ -21,6 +21,9 @@
 
   public function getOptions() {
     $manifest = PHUIIconView::getSheetManifest('main-header');
+    $custom_header_example =
+      PhabricatorCustomHeaderConfigType::getExampleConfig();
+    $experimental_link = 'https://secure.phabricator.com/T4214';
 
     $options = array();
     foreach (array_keys($manifest) as $sprite_name) {
@@ -66,6 +69,31 @@
             "    omit this if you just want a piece of text, like a copyright ".
             "    notice."))
         ->addExample($example, pht('Basic Example')),
+      $this->newOption(
+        'ui.custom-header',
+        'custom:PhabricatorCustomHeaderConfigType',
+        null)
+        ->setSummary(
+          pht('Customize the Phabricator logo.'))
+        ->setDescription(
+          pht('You can customize the Phabricator logo by specifying the '.
+              'phid for a viewable image you have uploaded to Phabricator '.
+              'via the [[ /file/ | Files application]]. This image should '.
+              'be:'."\n".
+              ' - 192px X 80px; while not enforced, images with these '.
+              'dimensions will look best across devices.'."\n".
+              ' - have view policy public if [[ '.
+              '/config/edit/policy.allow-public | `policy.allow-public`]] '.
+              'is true and otherwise view policy user; mismatches in these '.
+              'policy settings will result in a broken logo for some users.'.
+              "\n\n".
+              'You should restart your webserver after updating this value '.
+              'to see this change take effect.'.
+              "\n\n".
+              'As this feature is experimental, please read [[ %s | T4214 ]] '.
+              'for up to date information.',
+              $experimental_link))
+        ->addExample($custom_header_example, pht('Valid Config')),
     );
   }