diff --git a/wp-includes/class-wp-block-styles-registry.php b/wp-includes/class-wp-block-styles-registry.php
index df6945fd34..e95f7bf361 100644
--- a/wp-includes/class-wp-block-styles-registry.php
+++ b/wp-includes/class-wp-block-styles-registry.php
@@ -36,7 +36,7 @@ final class WP_Block_Styles_Registry {
 	 *
 	 * @param string $block_name       Block type name including namespace.
 	 * @param array  $style_properties Array containing the properties of the style name, label,
-	 *                                 style (name of the stylesheet to be enqueued),
+	 *                                 is_default, style_handle (name of the stylesheet to be enqueued),
 	 *                                 inline_style (string containing the CSS to be added).
 	 * @return bool True if the block style was registered with success and false otherwise.
 	 */
diff --git a/wp-includes/script-loader.php b/wp-includes/script-loader.php
index 2d18f87415..47a75a1603 100644
--- a/wp-includes/script-loader.php
+++ b/wp-includes/script-loader.php
@@ -2303,15 +2303,17 @@ function enqueue_editor_block_styles_assets() {
 	$register_script_lines = array( '( function() {' );
 	foreach ( $block_styles as $block_name => $styles ) {
 		foreach ( $styles as $style_properties ) {
+			$block_style = array(
+				'name'  => $style_properties['name'],
+				'label' => $style_properties['label'],
+			);
+			if ( isset( $style_properties['is_default'] ) ) {
+				$block_style['isDefault'] = $style_properties['is_default'];
+			}
 			$register_script_lines[] = sprintf(
 				'	wp.blocks.registerBlockStyle( \'%s\', %s );',
 				$block_name,
-				wp_json_encode(
-					array(
-						'name'  => $style_properties['name'],
-						'label' => $style_properties['label'],
-					)
-				)
+				wp_json_encode( $block_style )
 			);
 		}
 	}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 1da5f8bc7b..38d9999d5f 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.8-alpha-50702';
+$wp_version = '5.8-alpha-50703';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.