diff --git a/wp-admin/includes/class-core-upgrader.php b/wp-admin/includes/class-core-upgrader.php
index 0629e0b8e1..7c1d5e9c10 100644
--- a/wp-admin/includes/class-core-upgrader.php
+++ b/wp-admin/includes/class-core-upgrader.php
@@ -13,6 +13,11 @@
  * It allows for WordPress to upgrade itself in combination with
  * the wp-admin/includes/update-core.php file.
  *
+ * Note: newly introduced functions and methods cannot be used here.
+ * All functions must be present in both the previous version being upgraded from,
+ * and the later version that's being installed (e.g. when rolling back Core)
+ * as this file is used in both.
+ *
  * @since 2.8.0
  * @since 4.6.0 Moved to its own file from wp-admin/includes/class-wp-upgrader.php.
  *
@@ -391,13 +396,13 @@ class Core_Upgrader extends WP_Upgrader {
 	 *
 	 * @since 3.7.0
 	 *
+	 * @global string $wp_version       The WordPress version string.
 	 * @global string $wp_local_package Locale code of the package.
 	 *
 	 * @return bool True if the checksums match, otherwise false.
 	 */
 	public function check_files() {
-		global $wp_local_package;
-		$wp_version = wp_get_wp_version();
+		global $wp_version, $wp_local_package;
 
 		$checksums = get_core_checksums( $wp_version, isset( $wp_local_package ) ? $wp_local_package : 'en_US' );
 
diff --git a/wp-admin/includes/update-core.php b/wp-admin/includes/update-core.php
index 639faba224..1a814aa5f8 100644
--- a/wp-admin/includes/update-core.php
+++ b/wp-admin/includes/update-core.php
@@ -2,6 +2,11 @@
 /**
  * WordPress core upgrade functionality.
  *
+ * Note: newly introduced functions and methods cannot be used here.
+ * All functions must be present in both the previous version being upgraded from,
+ * and the later version that's being installed (e.g. when rolling back Core)
+ * as this file is used in both.
+ *
  * @package WordPress
  * @subpackage Administration
  * @since 2.7.0
@@ -1539,12 +1544,12 @@ function update_core( $from, $to ) {
  *
  * @global array              $_old_requests_files Requests files to be preloaded.
  * @global WP_Filesystem_Base $wp_filesystem       WordPress filesystem subclass.
+ * @global string             $wp_version          The WordPress version string.
  *
  * @param string $to Path to old WordPress installation.
  */
 function _preload_old_requests_classes_and_interfaces( $to ) {
-	global $_old_requests_files, $wp_filesystem;
-	$wp_version = wp_get_wp_version();
+	global $_old_requests_files, $wp_filesystem, $wp_version;
 
 	/*
 	 * Requests was introduced in WordPress 4.6.
@@ -1587,14 +1592,14 @@ function _preload_old_requests_classes_and_interfaces( $to ) {
  *
  * @since 3.3.0
  *
- * @global string $pagenow The filename of the current screen.
+ * @global string $wp_version The WordPress version string.
+ * @global string $pagenow    The filename of the current screen.
  * @global string $action
  *
  * @param string $new_version
  */
 function _redirect_to_about_wordpress( $new_version ) {
-	global $pagenow, $action;
-	$wp_version = wp_get_wp_version();
+	global $wp_version, $pagenow, $action;
 
 	if ( version_compare( $wp_version, '3.4-RC1', '>=' ) ) {
 		return;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 7eb4c0009b..8b00edb316 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.7-beta1-59179';
+$wp_version = '6.7-beta1-59180';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.