diff --git a/css_editor.module b/css_editor.module
index 53b5a57..53b7710 100644
--- a/css_editor.module
+++ b/css_editor.module
@@ -51,6 +51,17 @@ function css_editor_form_system_theme_settings_alter(&$form, FormStateInterface
       '#type' => 'checkbox',
       '#default_value' => $config->get('enabled'),
     );
+    // Text box for custom file name
+    $form['css_editor']['custom_filename'] = array(
+      '#type' => 'textfield',
+      '#title' => t('Custom Filename (Optional)'),
+      '#default_value' => $config->get('custom_filename'),
+      '#size' => 60,
+      '#maxlength' => 128,
+      '#pattern' => '[A-Za-z0-9\-_]+',
+      '#required' => FALSE,
+      '#description' => t("If you want to save this CSS file with a custom filename, enter that filename here, omitting the file extension.<br/>The filename must include only letters, numbers, dashes, and underscores."),
+    );
     // Editor box.
     $form['css_editor']['css'] = array(
       '#type' => 'textarea',
@@ -96,6 +107,7 @@ function css_editor_form_system_theme_settings_alter(&$form, FormStateInterface
         'url' => $preview_url,
       ),
     );
+    
     // Attach CSS and Javascript libraries.
     $form['#attached']['library'][] = 'css_editor/codemirror';
     $form['#attached']['library'][] = 'css_editor/css_editor';
@@ -112,14 +124,29 @@ function _css_editor_theme_settings_form_submit($form, FormStateInterface $form_
   if ($theme) {
     // Save file.
     $path = 'public://css_editor';
-    $file = $path . DIRECTORY_SEPARATOR . $theme . '.css';
+    $oldPath = \Drupal::config('css_editor.theme.' . $theme)->get('path');
+
+    if (!empty($form_state->getValue(['css_editor', 'custom_filename']))) {
+      // custom path definition
+      $file = $path . DIRECTORY_SEPARATOR . $form_state->getValue(['css_editor', 'custom_filename']) . '.css';
+    } else {
+      $file = $path . DIRECTORY_SEPARATOR . $theme . '.css';
+    }
     if (\Drupal::service('file_system')->prepareDirectory($path, FileSystemInterface::CREATE_DIRECTORY | FileSystemInterface::MODIFY_PERMISSIONS)) {
       \Drupal::service('file_system')->saveData($form_state->getValue(['css_editor', 'css']), $file, FileSystemInterface::EXISTS_REPLACE);
       \Drupal::service('file_system')->chmod($file);
     }
+    // delete obsolete file
+    if ($oldPath!=$file) {
+      \Drupal::logger('css_editor')->notice("Attempting to delete an obsolete file: ".$oldPath);
+      \Drupal::service('file_system')->delete($oldPath);
+    }
+    \Drupal::logger('css_editor')->notice("Saving path: ".$oldPath);
+    
     // Save settings.
     \Drupal::configFactory()->getEditable('css_editor.theme.' . $theme)
       ->set('enabled', $form_state->getValue(['css_editor', 'enabled']))
+      ->set('custom_filename', $form_state->getValue(['css_editor', 'custom_filename']))
       ->set('plaintext_enabled', $form_state->getValue(['css_editor', 'plaintext_enabled']))
       ->set('autopreview_enabled', $form_state->getValue(['css_editor', 'autopreview_enabled']))
       ->set('css', $form_state->getValue(['css_editor', 'css']))