diff --git a/src/wp-includes/theme.php b/src/wp-includes/theme.php
index 304f27fdb6..9c20b6a06f 100644
--- a/src/wp-includes/theme.php
+++ b/src/wp-includes/theme.php
@@ -3679,6 +3679,22 @@ function _wp_keep_alive_customize_changeset_dependent_auto_drafts( $new_status,
 	}
 }
 
+/**
+ * Prepares the post formats when registering theme support.
+ *
+ * @since
+ *
+ * @access private
+ *
+ * @return array
+ */
+function _prepare_theme_post_formats( $formats ) {
+		$formats = is_array( $formats ) ? array_values( $formats[0] ) : array();
+		$formats = array_merge( array( 'standard' ), $formats );
+
+		return $formats;
+}
+
 /**
  * Creates the initial theme features when the 'setup_theme' action is fired.
  *
@@ -4003,12 +4019,7 @@ function create_initial_theme_features() {
 					),
 					'default' => array( 'standard' ),
 				),
-				'prepare_callback' => static function ( $formats ) {
-					$formats = is_array( $formats ) ? array_values( $formats[0] ) : array();
-					$formats = array_merge( array( 'standard' ), $formats );
-
-					return $formats;
-				},
+				'prepare_callback' => '_prepare_theme_post_formats',
 			),
 		)
 	);