diff --git a/toolkit/content/xul.css b/toolkit/content/xul.css
index ba7642c9264ac201fec7be1bd492bc778bb147a2..9e89735e8a0886183ae7ecf98e6ce08142bf3bbc 100644
--- a/toolkit/content/xul.css
+++ b/toolkit/content/xul.css
@@ -456,7 +456,8 @@ 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;
 }
