diff --git a/wp-admin/includes/upgrade.php b/wp-admin/includes/upgrade.php
index 48cd7be662..d389a330e8 100644
--- a/wp-admin/includes/upgrade.php
+++ b/wp-admin/includes/upgrade.php
@@ -1433,6 +1433,10 @@ function upgrade_420() {
 			$tables = $wpdb->tables( 'blog' );
 		} else {
 			$tables = $wpdb->tables( 'all' );
+			if ( defined( 'DO_NOT_UPGRADE_GLOBAL_TABLES' ) ) {
+				$global_tables = $wpdb->tables( 'global' );
+				$tables = array_diff_assoc( $tables, $global_tables );
+			}
 		}
 
 		foreach ( $tables as $table ) {
@@ -1596,7 +1600,7 @@ function upgrade_network() {
 
 	// 4.2
 	if ( $wp_current_db_version < 31351 && $wpdb->charset === 'utf8mb4' ) {
-		if ( ! ( defined( 'DO_NOT_UPGRADE_GLOBAL_TABLES' ) && DO_NOT_UPGRADE_GLOBAL_TABLES ) ) {
+		if ( ! defined( 'DO_NOT_UPGRADE_GLOBAL_TABLES' ) ) {
 			$wpdb->query( "ALTER TABLE $wpdb->usermeta DROP INDEX meta_key, ADD INDEX meta_key(meta_key(191))" );
 			$wpdb->query( "ALTER TABLE $wpdb->site DROP INDEX domain, ADD INDEX domain(domain(140),path(51))" );
 			$wpdb->query( "ALTER TABLE $wpdb->sitemeta DROP INDEX meta_key, ADD INDEX meta_key(meta_key(191))" );
@@ -1612,7 +1616,7 @@ function upgrade_network() {
 
 	// 4.2.2
 	if ( $wp_current_db_version < 31535 && 'utf8mb4' === $wpdb->charset ) {
-		if ( ! ( defined( 'DO_NOT_UPGRADE_GLOBAL_TABLES' ) && DO_NOT_UPGRADE_GLOBAL_TABLES ) ) {
+		if ( ! defined( 'DO_NOT_UPGRADE_GLOBAL_TABLES' ) ) {
 			$upgrade = false;
 			$indexes = $wpdb->get_results( "SHOW INDEXES FROM $wpdb->signups" );
 			foreach( $indexes as $index ) {
@@ -2459,7 +2463,7 @@ function pre_schema_upgrade() {
 
 	// Upgrade versions prior to 4.2.
 	if ( $wp_current_db_version < 31351 ) {
-		if ( ! is_multisite() ) {
+		if ( ! is_multisite() && ! defined( 'DO_NOT_UPGRADE_GLOBAL_TABLES' ) ) {
 			$wpdb->query( "ALTER TABLE $wpdb->usermeta DROP INDEX meta_key, ADD INDEX meta_key(meta_key(191))" );
 		}
 		$wpdb->query( "ALTER TABLE $wpdb->terms DROP INDEX slug, ADD INDEX slug(slug(191))" );