diff --git a/lib/block-supports/layout.php b/lib/block-supports/layout.php
index e01a3c60ce927a..92f28ba6950a51 100644
--- a/lib/block-supports/layout.php
+++ b/lib/block-supports/layout.php
@@ -53,7 +53,7 @@ function gutenberg_get_layout_style( $selector, $layout, $has_block_gap_support
 
 		$style = '';
 		if ( $content_size || $wide_size ) {
-			$style  = "$selector > :not(.alignleft):not(.alignright) {";
+			$style  = "$selector > :where(:not(.alignleft):not(.alignright)) {";
 			$style .= 'max-width: ' . esc_html( $all_max_width_value ) . ';';
 			$style .= 'margin-left: auto !important;';
 			$style .= 'margin-right: auto !important;';
diff --git a/packages/block-editor/src/layouts/flow.js b/packages/block-editor/src/layouts/flow.js
index f5581534fa7995..ae2e9379bdf110 100644
--- a/packages/block-editor/src/layouts/flow.js
+++ b/packages/block-editor/src/layouts/flow.js
@@ -115,7 +115,10 @@ export default {
 		let output =
 			!! contentSize || !! wideSize
 				? `
-					${ appendSelectors( selector, '> :not(.alignleft):not(.alignright)' ) } {
+					${ appendSelectors(
+						selector,
+						'> :where(:not(.alignleft):not(.alignright))'
+					) } {
 						max-width: ${ contentSize ?? wideSize };
 						margin-left: auto !important;
 						margin-right: auto !important;