diff --git modules/search/search.module modules/search/search.module
index a698c52..dc8d668 100644
--- modules/search/search.module
+++ modules/search/search.module
@@ -951,6 +951,12 @@ function search_box_form_submit($form, &$form_state) {
     unset($_GET['destination']);
   }
 
+  $keys = $form_state['values']['search_block_form'];
+  if ($keys == '') {
+    form_set_error('keys', t('Please enter some keywords.'));
+    // Fall through to the form redirect.
+  }
+
   $form_id = $form['form_id']['#value'];
   $form_state['redirect'] = 'search/node/' . trim($form_state['values'][$form_id]);
 }