diff --git a/layout/style/res/scrollbars.css b/layout/style/res/scrollbars.css
index ebedd90a3f21..a4f26118889b 100644
--- a/layout/style/res/scrollbars.css
+++ b/layout/style/res/scrollbars.css
@@ -21,6 +21,7 @@
     -moz-control-character-visibility: initial;
     -moz-min-font-size-ratio: initial;
     -moz-box-collapse: initial;
+    -moz-theme: initial;
 
     /* We don't want zoom on our ancestors to affect our styles. */
     zoom: document;
diff --git a/toolkit/themes/shared/in-content/common-shared.css b/toolkit/themes/shared/in-content/common-shared.css
index ab1500b8e433..d123d3c3b01a 100644
--- a/toolkit/themes/shared/in-content/common-shared.css
+++ b/toolkit/themes/shared/in-content/common-shared.css
@@ -104,6 +104,7 @@
   --card-outline-color: var(--grey-30);
   --card-shadow-hover: var(--card-shadow), 0 0 0 5px var(--card-outline-color);
 
+  -moz-theme: non-native;
   accent-color: var(--in-content-accent-color);
   color-scheme: light dark;
 }