Index: wysiwyg_filter.admin.inc
===================================================================
--- wysiwyg_filter.admin.inc	(revision 493)
+++ wysiwyg_filter.admin.inc	(working copy)
@@ -145,13 +145,24 @@
     '#description' => t('Enter a comma separated list of top level domain names. Note that all subdomains will also be included. Example: example.com will match example.com, www.example.com, etc.'),
   );
 
-  $form['#validate'] = array('wysiwyg_filter_settings_filter_validate');
-  $form['#submit'] = array('wysiwyg_filter_settings_filter_submit');
-
   return $form;
 }
 
 /**
+ * Implementation of hook_form_FORM_ID_alter().
+ *
+ * Because filter format forms are merged, any common keys need to be added in 
+ * a form_alter. Otherwise, e.g. submit handlers added by one module would be overwritten
+ * by those of another module.
+ */
+function wysiwyg_filter_form_filter_admin_configure_alter(&$form, $form_state) {
+  if (isset($form['wysiwyg_filter'])) {
+    $form['#validate'][] = 'wysiwyg_filter_settings_filter_validate';
+    $form['#submit'][] = 'wysiwyg_filter_settings_filter_submit';
+  }
+}
+
+/**
  * Validate if the given rule definition is complete.
  *
  * @param $rule_info