diff --git a/toolkit/content/xul.css b/toolkit/content/xul.css
index badef34e6072da6e0e1180f5f08ab201a89fa195..2842eee9d5655444ccac8c085f19df0247886d64 100644
--- a/toolkit/content/xul.css
+++ b/toolkit/content/xul.css
@@ -461,7 +461,8 @@ deck > *|*:not(:-moz-native-anonymous) {
 }
 
 tabpanels > .deck-selected,
-deck > .deck-selected {
+deck > .deck-selected,
+tabpanels > [zen-split="true"] {
   -moz-subtree-hidden-only-visually: 0;
   visibility: inherit;
 }