diff --git a/modules/firefox.nix b/modules/firefox.nix
index fba58d0..7b10ac0 100644
--- a/modules/firefox.nix
+++ b/modules/firefox.nix
@@ -110,6 +110,7 @@
     // appearance
     lockPref("sidebar.revamp", true);
     lockPref("sidebar.verticalTabs", true);
+    lockPref("sidebar.revamp.round-content-area", true);
     lockPref("sidebar.animation.enabled", false);
     lockPref("extensions.activeThemeID", "firefox-compact-dark@mozilla.org");
     lockPref("browser.toolbars.bookmarks.visibility", "newtab");