diff --git a/modules/block/block.module b/modules/block/block.module
index e2cce6b..2af4c88 100644
--- a/modules/block/block.module
+++ b/modules/block/block.module
@@ -613,13 +613,14 @@ function block_form_user_profile_form_alter(&$form, &$form_state) {
  * Implements hook_field_extra_fields().
  */
 function block_field_extra_fields() {
-  $extra['user']['user']['form']['block'] = array(
-    'label' => t('Personalize blocks'),
-    'description' => t('Block module form element.'),
-    'weight' => 3,
-  );
-
-  return $extra;
+  if (variable_get('drupal_enable_core_extra_fields')) {
+    $extra['user']['user']['form']['block'] = array(
+      'label' => t('Personalize blocks'),
+      'description' => t('Block module form element.'),
+      'weight' => 3,
+    );
+    return $extra;
+  }
 }
 
 /**
diff --git a/modules/contact/contact.module b/modules/contact/contact.module
index 54711b3..8717635 100644
--- a/modules/contact/contact.module
+++ b/modules/contact/contact.module
@@ -262,11 +262,12 @@ function contact_form_user_admin_settings_alter(&$form, &$form_state) {
  * Implements hook_field_extra_fields().
  */
 function contact_field_extra_fields() {
-  $extra['user']['user']['form']['contact'] = array(
-    'label' => t('Contact settings'),
-    'description' => t('Contact module form element.'),
-    'weight' => 5,
-  );
-
-  return $extra;
+  if (variable_get('drupal_enable_core_extra_fields')) {
+    $extra['user']['user']['form']['contact'] = array(
+      'label' => t('Contact settings'),
+      'description' => t('Contact module form element.'),
+      'weight' => 5,
+    );
+    return $extra;
+  }
 }
diff --git a/modules/locale/locale.module b/modules/locale/locale.module
index 9bd39fb..f2ca381 100644
--- a/modules/locale/locale.module
+++ b/modules/locale/locale.module
@@ -323,13 +323,14 @@ function locale_form_path_admin_form_alter(&$form, &$form_state) {
  * Implements hook_field_extra_fields().
  */
 function locale_field_extra_fields() {
-  $extra['user']['user']['form']['locale'] = array(
-    'label' => t('Language settings'),
-    'description' => t('Locale module form element.'),
-    'weight' => 1,
-  );
-
-  return $extra;
+  if (variable_get('drupal_enable_core_extra_fields')) {
+    $extra['user']['user']['form']['locale'] = array(
+      'label' => t('Language settings'),
+      'description' => t('Locale module form element.'),
+      'weight' => 1,
+    );
+    return $extra;
+  }
 }
 
 /**
diff --git a/modules/overlay/overlay.module b/modules/overlay/overlay.module
index cf24d8c..0c57b37 100644
--- a/modules/overlay/overlay.module
+++ b/modules/overlay/overlay.module
@@ -120,13 +120,14 @@ function overlay_form_user_profile_form_alter(&$form, &$form_state) {
  * Implements hook_field_extra_fields().
  */
 function overlay_field_extra_fields() {
-  $extra['user']['user']['form']['overlay_control'] = array(
-    'label' => t('Administrative overlay'),
-    'description' => t('Overlay module form element.'),
-    'weight' => 4,
-  );
-
-  return $extra;
+  if (variable_get('drupal_enable_core_extra_fields')) {
+    $extra['user']['user']['form']['overlay_control'] = array(
+      'label' => t('Administrative overlay'),
+      'description' => t('Overlay module form element.'),
+      'weight' => 4,
+    );
+    return $extra;
+  }
 }
 
 /**
diff --git a/modules/user/user.module b/modules/user/user.module
index 00601b1..fbac127 100644
--- a/modules/user/user.module
+++ b/modules/user/user.module
@@ -212,49 +212,51 @@ function user_field_info_alter(&$info) {
  * Implements hook_field_extra_fields().
  */
 function user_field_extra_fields() {
-  $extra['user']['user'] = array(
-    'form' => array(
-      'account' => array(
-        'label' => t('User name and password'),
-        'description' => t('User module account form elements.'),
-        'weight' => -10,
-      ),
-      'timezone' => array(
-        'label' => t('Timezone'),
-        'description' => t('User module timezone form element.'),
-        'weight' => 6,
-      ),
-    ),
-    'display' => array(
-      'summary' => array(
-        'label' => t('History'),
-        'description' => t('User module history view element.'),
-        'weight' => 5,
+  if (variable_get('drupal_enable_core_extra_fields')) {
+    $extra['user']['user'] = array(
+      'form' => array(
+        'account' => array(
+          'label' => t('User name and password'),
+          'description' => t('User module account form elements.'),
+          'weight' => -10,
+        ),
+        'timezone' => array(
+          'label' => t('Timezone'),
+          'description' => t('User module timezone form element.'),
+          'weight' => 6,
+        ),
       ),
-    ),
-  );
-
-  if (variable_get('user_pictures', 0)) {
-    $extra['user']['user']['form'] += array(
-      'picture' => array(
-        'label' => t('User picture'),
-        'description' => t('User module picture form element.'),
-        'weight' => 1,
+      'display' => array(
+        'summary' => array(
+          'label' => t('History'),
+          'description' => t('User module history view element.'),
+          'weight' => 5,
+        ),
       ),
     );
-  }
 
-  if (variable_get('user_signatures', 0)) {
-    $extra['user']['user']['form'] += array(
-      'signature_settings' => array(
-        'label' => t('Signature settings'),
-        'description' => t('User module form element.'),
-        'weight' => 1,
-      ),
-    );
-  }
+    if (variable_get('user_pictures', 0)) {
+      $extra['user']['user']['form'] += array(
+        'picture' => array(
+          'label' => t('User picture'),
+          'description' => t('User module picture form element.'),
+          'weight' => 1,
+        ),
+      );
+    }
 
-  return $extra;
+    if (variable_get('user_signatures', 0)) {
+      $extra['user']['user']['form'] += array(
+        'signature_settings' => array(
+          'label' => t('Signature settings'),
+          'description' => t('User module form element.'),
+          'weight' => 1,
+        ),
+      );
+    }
+
+    return $extra;
+  }
 }
 
 /**