diff --git a/domain_fields.admin.inc b/domain_fields.admin.inc
index b8c0f12..f481f8a 100644
--- a/domain_fields.admin.inc
+++ b/domain_fields.admin.inc
@@ -92,24 +92,24 @@ function domain_fields_settings_form($form, &$form_state, $domain, $entity_type
  * Submit handler to reset all of the domains field settings.
  */
 function domain_fields_settings_form_reset_submit($form, &$form_state) {
-  $domain_id = $form_state['domain']['domain_id'];
+  $machine_name = $form_state['domain']['machine_name'];
   $entity_type = $form_state['entity_type'];
 
-  $settings = variable_get('domain_fields_' . $domain_id, array());
+  $settings = variable_get('domain_fields_' . $machine_name, array());
   $settings[$entity_type] = array();
-  variable_set('domain_fields_' . $domain_id, $settings);
+  variable_set('domain_fields_' . $machine_name, $settings);
 }
 
 /**
  * Submit handler to save all of the domains field settings.
  */
 function domain_fields_settings_form_save_submit($form, &$form_state) {
-  $domain_id = $form_state['domain']['domain_id'];
+  $machine_name = $form_state['domain']['machine_name'];
   $entity_type = $form_state['entity_type'];
 
-  $settings = variable_get('domain_fields_' . $domain_id, array());
+  $settings = variable_get('domain_fields_' . $machine_name, array());
   $settings[$entity_type] = $form_state['values'][$entity_type];
-  variable_set('domain_fields_' . $domain_id, $settings);
+  variable_set('domain_fields_' . $machine_name, $settings);
 }
 
 /**
diff --git a/domain_fields.install b/domain_fields.install
index 785dbfb..02cd7ac 100644
--- a/domain_fields.install
+++ b/domain_fields.install
@@ -20,3 +20,20 @@ function domain_fields_update_7002() {
   variable_set('menu_rebuild_needed', TRUE);
   return t('Menu links are queued to be rebuilt.');
 }
+
+/**
+ * Update names of domain_fields_* variables.
+ */
+function domain_fields_update_7003() {
+  $domains = domain_domains();
+  foreach ($domains as $domain) {
+    $old_settings = variable_get('domain_fields_' . $domain['domain_id'], array());
+    $new_settings = variable_get('domain_fields_' . $domain['machine_name'], array());
+
+    if ($old_settings && empty($new_settings)) {
+      variable_set('domain_fields_' . $domain['machine_name'], $old_settings);
+    }
+
+    variable_del('domain_fields_' . $domain['domain_id']);
+  }
+}
diff --git a/domain_fields.module b/domain_fields.module
index aa0efe4..dc62af3 100644
--- a/domain_fields.module
+++ b/domain_fields.module
@@ -102,7 +102,7 @@ function domain_fields_settings($domain = NULL) {
     $domain = domain_get_domain();
   }
 
-  return variable_get('domain_fields_' . $domain['domain_id'], array());
+  return variable_get('domain_fields_' . $domain['machine_name'], array());
 }
 
 /**