diff --git a/css/r11form.css b/css/r11form.css
index 4d5c135..923a091 100644
--- a/css/r11form.css
+++ b/css/r11form.css
@@ -420,4 +420,9 @@
 
 .hiddable.active {
     display: inherit;
+}
+
+/* In case of collision with classes that use 'active' */
+.hidden {
+    display: none;
 }
\ No newline at end of file