diff --git a/src/common/optionsPrototype.json5 b/src/common/optionsPrototype.json5
index 6b6e01b..0854647 100644
--- a/src/common/optionsPrototype.json5
+++ b/src/common/optionsPrototype.json5
@@ -151,6 +151,11 @@
     context: 'experiments',
     killSwitchType: 'experiment',
   },
+  'uispacing': {
+    defaultValue: false,
+    context: 'experiments',
+    killSwitchType: 'experiment',
+  },
 
   // Internal options:
   'ccdarktheme_switch_enabled': {