diff --git a/src/wp-includes/default-filters.php b/src/wp-includes/default-filters.php
index 4e6340700c..2345f19059 100644
--- a/src/wp-includes/default-filters.php
+++ b/src/wp-includes/default-filters.php
@@ -557,7 +557,7 @@ add_action( 'wp_default_scripts', 'wp_default_packages' );
 
 add_action( 'wp_enqueue_scripts', 'wp_localize_jquery_ui_datepicker', 1000 );
 add_action( 'wp_enqueue_scripts', 'wp_common_block_scripts_and_styles' );
-add_action( 'wp_enqueue_scripts', 'wp_enqueue_classic_theme_styles' );
+add_action( 'wp_head', 'wp_enqueue_classic_theme_styles' );
 add_action( 'admin_enqueue_scripts', 'wp_localize_jquery_ui_datepicker', 1000 );
 add_action( 'admin_enqueue_scripts', 'wp_common_block_scripts_and_styles' );
 add_action( 'enqueue_block_assets', 'wp_enqueue_registered_block_scripts_and_styles' );
diff --git a/src/wp-includes/script-loader.php b/src/wp-includes/script-loader.php
index de52578936..1af6c0364f 100644
--- a/src/wp-includes/script-loader.php
+++ b/src/wp-includes/script-loader.php
@@ -3667,10 +3667,21 @@ function _wp_theme_json_webfonts_handler() {
  * @since 6.1.0
  */
 function wp_enqueue_classic_theme_styles() {
-	if ( ! wp_theme_has_theme_json() ) {
-		$suffix = wp_scripts_get_suffix();
-		wp_register_style( 'classic-theme-styles', '/' . WPINC . "/css/classic-themes$suffix.css", array(), true );
-		wp_enqueue_style( 'classic-theme-styles' );
+	if ( ! wp_theme_has_theme_json() ) {?>
+		<style>
+			.wp-block-button__link {
+			color: #ffffff;
+			background-color: #32373c;
+			border-radius: 9999px; /* 100% causes an oval, but any explicit but really high value retains the pill shape. */
+			/* This needs a low specificity so it won't override the rules from the button element if defined in theme.json. */
+			box-shadow: none;
+			text-decoration: none;
+			/* The extra 2px are added to size solids the same as the outline versions.*/
+			padding: calc(0.667em + 2px) calc(1.333em + 2px);
+			font-size: 1.125em;
+		}
+		</style>
+		<?php
 	}
 }