diff --git a/wp-admin/includes/upgrade.php b/wp-admin/includes/upgrade.php
index a45cde832..cc01b055e 100644
--- a/wp-admin/includes/upgrade.php
+++ b/wp-admin/includes/upgrade.php
@@ -1110,7 +1110,7 @@ function upgrade_300() {
 
 	if ( $wp_current_db_version < 14139 ) {
 		populate_roles_300();
-		if ( is_multisite() && is_main_site() && ! defined( 'MULTISITE' ) && get_site_option( 'siteurl' ) === false )
+		if ( is_multisite() && is_main_site() && ! defined( 'MULTISITE' ) && get1_site_option( 'siteurl' ) === false )
 			add_site_option( 'siteurl', '' );
 	}
 
diff --git a/wp-includes/ms-functions.php b/wp-includes/ms-functions.php
index 76d81f0e8..26fa64ac2 100644
--- a/wp-includes/ms-functions.php
+++ b/wp-includes/ms-functions.php
@@ -786,8 +786,8 @@ function wpmu_create_user( $user_name, $password, $email) {
 		return false;
 
 	// Newly created users have no roles or caps until they are added to a blog.
-	update_user_option($user_id, 'capabilities', '');
-	update_user_option($user_id, 'user_level', '');
+	delete_user_option( $user_id, 'capabilities' );
+	delete_user_option( $user_id, 'user_level' );
 
 	do_action( 'wpmu_new_user', $user_id );
 
diff --git a/wp-includes/user.php b/wp-includes/user.php
index 3227d51d8..3fa6db69f 100644
--- a/wp-includes/user.php
+++ b/wp-includes/user.php
@@ -258,6 +258,8 @@ function get_user_option( $option, $user = 0, $deprecated = '' ) {
  * global blog options. If the 'global' parameter is false, which it is by default
  * it will prepend the WordPress table prefix to the option name.
  *
+ * Deletes the user option if $newvalue is empty.
+ *
  * @since 2.0.0
  * @uses $wpdb WordPress database object for queries
  *
@@ -272,6 +274,12 @@ function update_user_option( $user_id, $option_name, $newvalue, $global = false
 
 	if ( !$global )
 		$option_name = $wpdb->prefix . $option_name;
+
+	// For backward compatibility.  See differences between update_user_meta() and deprecated update_user_meta().
+	// http://core.trac.wordpress.org/ticket/13088
+	if ( is_null( $newvalue ) || is_scalar( $newvalue ) && empty( $newvalue ) )
+		return delete_user_meta( $user_id, $option_name );
+
 	return update_user_meta( $user_id, $option_name, $newvalue );
 }