diff --git a/mu-plugins/blocks/sidebar-container/postcss/style.pcss b/mu-plugins/blocks/sidebar-container/postcss/style.pcss
index 311653fc0..ec89ab474 100644
--- a/mu-plugins/blocks/sidebar-container/postcss/style.pcss
+++ b/mu-plugins/blocks/sidebar-container/postcss/style.pcss
@@ -102,6 +102,6 @@ main .wp-block-wporg-sidebar-container {
 }
 
 /* Set up the custom properties. These can be overridden by settings in theme.json. */
-:where(body) {
+:where(html) {
 	--wp--custom--wporg-sidebar-container--spacing--margin--top: var(--wp--preset--spacing--edge-space);
 }