diff --git a/boost.module b/boost.module
index a6b3db2eb69cb481a50307f98ffbead65e81dc19..ce80a723be47ac900571e1cbb72aacd133842db5 100644
--- a/boost.module
+++ b/boost.module
@@ -260,6 +260,17 @@ function boost_init() {
   }
 }
 
+/**
+ * Implements hook_form_alter().
+ */
+function boost_form_alter(&$form, &$form_state, $form_id) {
+  global $_boost;
+
+  if (! empty($_boost['cache_this'])) {
+    $form['#immutable'] = TRUE;
+  }
+}
+
 /**
  * Implements hook_drupal_goto_alter().
  */