diff --git a/src/wp-includes/class-wp-theme-json.php b/src/wp-includes/class-wp-theme-json.php
index 588aeaa89e38e..a03c51c617444 100644
--- a/src/wp-includes/class-wp-theme-json.php
+++ b/src/wp-includes/class-wp-theme-json.php
@@ -205,6 +205,15 @@ class WP_Theme_JSON {
 			'classes'           => array(),
 			'properties'        => array( 'box-shadow' ),
 		),
+		array(
+			'path'              => array( 'border', 'radiusSizes' ),
+			'prevent_override'  => false,
+			'use_default_names' => false,
+			'value_key'         => 'size',
+			'css_vars'          => '--wp--preset--border-radius--$slug',
+			'classes'           => array(),
+			'properties'        => array( 'border-radius' ),
+		),
 	);
 
 	/**
diff --git a/src/wp-includes/style-engine/class-wp-style-engine.php b/src/wp-includes/style-engine/class-wp-style-engine.php
index 1234efdc6447a..f47c349aecbe3 100644
--- a/src/wp-includes/style-engine/class-wp-style-engine.php
+++ b/src/wp-includes/style-engine/class-wp-style-engine.php
@@ -142,6 +142,9 @@ final class WP_Style_Engine {
 					'individual' => 'border-%s-radius',
 				),
 				'path'          => array( 'border', 'radius' ),
+				'css_vars'      => array(
+					'border-radius' => '--wp--preset--border-radius--$slug',
+				),
 			),
 			'style'  => array(
 				'property_keys' => array(