Index: src/wp-admin/includes/upgrade.php
===================================================================
--- src/wp-admin/includes/upgrade.php	(revision 41286)
+++ src/wp-admin/includes/upgrade.php	(working copy)
@@ -433,10 +433,10 @@
 	wp_cache_flush();
 
 	if ( is_multisite() ) {
-		if ( $wpdb->get_row( "SELECT blog_id FROM {$wpdb->blog_versions} WHERE blog_id = '{$wpdb->blogid}'" ) )
-			$wpdb->query( "UPDATE {$wpdb->blog_versions} SET db_version = '{$wp_db_version}' WHERE blog_id = '{$wpdb->blogid}'" );
+		if ( $wpdb->get_row( $wpdb->prepare( 'SELECT blog_id FROM %s WHERE blog_id = %d', $wpdb->blog_versions, get_current_blog_id() ) ) )
+			$wpdb->query( $wpdb->prepare( 'UPDATE %s SET db_version = %d WHERE blog_id = %d', $wpdb->blog_versions, $wp_db_version, get_current_blog_id() ) );
 		else
-			$wpdb->query( "INSERT INTO {$wpdb->blog_versions} ( `blog_id` , `db_version` , `last_updated` ) VALUES ( '{$wpdb->blogid}', '{$wp_db_version}', NOW());" );
+			$wpdb->query( $wpdb->prepare( 'INSERT INTO %s ( `blog_id` , `db_version` , `last_updated` ) VALUES ( %d, %d, %s);', get_current_blog_id(), $wpdb->blog_versions, $wp_db_version, NOW() ) );
 	}
 
 	/**
@@ -1257,7 +1257,7 @@
 			}
 			$start += 20;
 		}
-		refresh_blog_details( $wpdb->blogid );
+		refresh_blog_details( get_current_blog_id() );
 	}
 }
 
Index: src/wp-admin/ms-delete-site.php
===================================================================
--- src/wp-admin/ms-delete-site.php	(revision 41286)
+++ src/wp-admin/ms-delete-site.php	(working copy)
@@ -17,7 +17,7 @@
 
 if ( isset( $_GET['h'] ) && $_GET['h'] != '' && get_option( 'delete_blog_hash' ) != false ) {
 	if ( hash_equals( get_option( 'delete_blog_hash' ), $_GET['h'] ) ) {
-		wpmu_delete_blog( $wpdb->blogid );
+		wpmu_delete_blog( get_current_blog_id() );
 		wp_die( sprintf( __( 'Thank you for using %s, your site has been deleted. Happy trails to you until we meet again.' ), get_network()->site_name ) );
 	} else {
 		wp_die( __( "I'm sorry, the link you clicked is stale. Please select another option." ) );
Index: src/wp-admin/user-new.php
===================================================================
--- src/wp-admin/user-new.php	(revision 41286)
+++ src/wp-admin/user-new.php	(working copy)
@@ -156,7 +156,7 @@
 				add_filter( 'wpmu_signup_user_notification', '__return_false' ); // Disable confirmation email
 				add_filter( 'wpmu_welcome_user_notification', '__return_false' ); // Disable welcome email
 			}
-			wpmu_signup_user( $new_user_login, $new_user_email, array( 'add_to_blog' => $wpdb->blogid, 'new_role' => $_REQUEST['role'] ) );
+			wpmu_signup_user( $new_user_login, $new_user_email, array( 'add_to_blog' => get_current_blog_id(), 'new_role' => $_REQUEST['role'] ) );
 			if ( isset( $_POST[ 'noconfirmation' ] ) && current_user_can( 'manage_network_users' ) ) {
 				$key = $wpdb->get_var( $wpdb->prepare( "SELECT activation_key FROM {$wpdb->signups} WHERE user_login = %s AND user_email = %s", $new_user_login, $new_user_email ) );
 				$new_user = wpmu_activate_signup( $key );
Index: src/wp-includes/ms-blogs.php
===================================================================
--- src/wp-includes/ms-blogs.php	(revision 41286)
+++ src/wp-includes/ms-blogs.php	(working copy)
@@ -12,13 +12,10 @@
  * Update the last_updated field for the current site.
  *
  * @since MU (3.0.0)
- *
- * @global wpdb $wpdb WordPress database abstraction object.
  */
 function wpmu_update_blogs_date() {
-	global $wpdb;
 
-	update_blog_details( $wpdb->blogid, array('last_updated' => current_time('mysql', true)) );
+	update_blog_details( get_current_blog_id(), array('last_updated' => current_time('mysql', true)) );
 	/**
 	 * Fires after the blog details are updated.
 	 *
@@ -26,7 +23,7 @@
 	 *
 	 * @param int $blog_id Site ID.
 	 */
-	do_action( 'wpmu_blog_updated', $wpdb->blogid );
+	do_action( 'wpmu_blog_updated', get_current_blog_id() );
 }
 
 /**
Index: src/wp-includes/ms-default-constants.php
===================================================================
--- src/wp-includes/ms-default-constants.php	(revision 41286)
+++ src/wp-includes/ms-default-constants.php	(working copy)
@@ -14,11 +14,8 @@
  * wp-includes/ms-files.php (wp-content/blogs.php in MU).
  *
  * @since 3.0.0
- *
- * @global wpdb $wpdb WordPress database abstraction object.
  */
 function ms_upload_constants() {
-	global $wpdb;
 
 	// This filter is attached in ms-default-filters.php but that file is not included during SHORTINIT.
 	add_filter( 'default_site_option_ms_files_rewriting', '__return_true' );
@@ -33,11 +30,11 @@
 	// Note, the main site in a post-MU network uses wp-content/uploads.
 	// This is handled in wp_upload_dir() by ignoring UPLOADS for this case.
 	if ( ! defined( 'UPLOADS' ) ) {
-		define( 'UPLOADS', UPLOADBLOGSDIR . "/{$wpdb->blogid}/files/" );
+		define( 'UPLOADS', UPLOADBLOGSDIR . '/' . get_current_blog_id() . '/files/' );
 
 		// Uploads dir relative to ABSPATH
 		if ( 'wp-content/blogs.dir' == UPLOADBLOGSDIR && ! defined( 'BLOGUPLOADDIR' ) )
-			define( 'BLOGUPLOADDIR', WP_CONTENT_DIR . "/blogs.dir/{$wpdb->blogid}/files/" );
+			define( 'BLOGUPLOADDIR', WP_CONTENT_DIR . '/blogs.dir/' . get_current_blog_id() . '/files/' );
 	}
 }
 
Index: src/wp-includes/ms-functions.php
===================================================================
--- src/wp-includes/ms-functions.php	(revision 41286)
+++ src/wp-includes/ms-functions.php	(working copy)
@@ -34,19 +34,16 @@
  *
  * @since MU (3.0.0) 1.0
  *
- * @global wpdb $wpdb WordPress database abstraction object.
- *
  * @param int $user_id The unique ID of the user
  * @return WP_Site|void The blog object
  */
 function get_active_blog_for_user( $user_id ) {
-	global $wpdb;
 	$blogs = get_blogs_of_user( $user_id );
 	if ( empty( $blogs ) )
 		return;
 
 	if ( !is_multisite() )
-		return $blogs[$wpdb->blogid];
+		return $blogs[get_current_blog_id()];
 
 	$primary_blog = get_user_meta( $user_id, 'primary_blog', true );
 	$first_blog = current($blogs);
@@ -2216,7 +2213,7 @@
 
 	$current_user = wp_get_current_user();
 	if ( $blog_id == 0 ) {
-		$blog_id = $wpdb->blogid;
+		$blog_id = get_current_blog_id();
 	}
 	$local_key = $wpdb->get_blog_prefix( $blog_id ) . $key;
 
Index: tests/phpunit/tests/multisite/site.php
===================================================================
--- tests/phpunit/tests/multisite/site.php	(revision 41286)
+++ tests/phpunit/tests/multisite/site.php	(working copy)
@@ -348,7 +348,7 @@
 		wpmu_update_blogs_date();
 
 		// compare the update time with the current time, allow delta < 2
-		$blog = get_site( $wpdb->blogid );
+		$blog = get_site( get_current_blog_id() );
 		$current_time = time();
 		$time_difference = $current_time - strtotime( $blog->last_updated );
 		$this->assertLessThan( 2, $time_difference );
Index: tests/phpunit/tests/user/multisite.php
===================================================================
--- tests/phpunit/tests/user/multisite.php	(revision 41286)
+++ tests/phpunit/tests/user/multisite.php	(working copy)
@@ -120,7 +120,7 @@
 		wp_set_current_user( $user1_id );
 
 		$this->assertTrue( is_blog_user() );
-		$this->assertTrue( is_blog_user( $wpdb->blogid ) );
+		$this->assertTrue( is_blog_user( get_current_blog_id() ) );
 
 		$blog_ids = array();
 
@@ -152,9 +152,9 @@
 
 		$this->assertTrue( is_user_member_of_blog() );
 		$this->assertTrue( is_user_member_of_blog( 0, 0 ) );
-		$this->assertTrue( is_user_member_of_blog( 0, $wpdb->blogid ) );
+		$this->assertTrue( is_user_member_of_blog( 0, get_current_blog_id() ) );
 		$this->assertTrue( is_user_member_of_blog( $user1_id ) );
-		$this->assertTrue( is_user_member_of_blog( $user1_id, $wpdb->blogid ) );
+		$this->assertTrue( is_user_member_of_blog( $user1_id, get_current_blog_id() ) );
 
 		$blog_ids = self::factory()->blog->create_many( 1 );
 		foreach ( $blog_ids as $blog_id ) {