diff --git a/wp-admin/ms-edit.php b/wp-admin/ms-edit.php
index 7a23d1f18..19a1e5d61 100644
--- a/wp-admin/ms-edit.php
+++ b/wp-admin/ms-edit.php
@@ -235,12 +235,12 @@ switch ( $_GET['action'] ) {
 			$newroles = $_POST[ 'role' ];
 			reset( $newroles );
 			foreach ( (array) $newroles as $userid => $role ) {
-				$role_len = strlen( $role );
-				$existing_role = $wpdb->get_var( "SELECT meta_value FROM $wpdb->usermeta WHERE user_id = '$userid'  AND meta_key = '" . $blog_prefix. "capabilities'" );
-				if ( false == $existing_role )
-					$wpdb->query( "INSERT INTO " . $wpdb->usermeta . "( `umeta_id` , `user_id` , `meta_key` , `meta_value` ) VALUES ( NULL, '$userid', '" . $blog_prefix . "capabilities', 'a:1:{s:" . strlen( $role ) . ":\"" . $role . "\";b:1;}')" );
-				elseif ( $existing_role != "a:1:{s:" . strlen( $role ) . ":\"" . $role . "\";b:1;}" )
-					$wpdb->query( "UPDATE $wpdb->usermeta SET meta_value = 'a:1:{s:" . strlen( $role ) . ":\"" . $role . "\";b:1;}' WHERE user_id = '$userid'  AND meta_key = '" . $blog_prefix . "capabilities'" );
+				$user = new WP_User($userid);
+				if ( ! $user )
+					continue;
+				// Hack. Init user caps for given blog.
+				$user->_init_caps($blog_prefix . 'capabilities');
+				$user->set_role($role);
 			}
 		}
 
diff --git a/wp-includes/capabilities.php b/wp-includes/capabilities.php
index 47f7d71b2..ffc49da01 100644
--- a/wp-includes/capabilities.php
+++ b/wp-includes/capabilities.php
@@ -508,11 +508,16 @@ class WP_User {
 	 * used.
 	 *
 	 * @since 2.1.0
+	 *
+	 * @param string $cap_key Optional capability key
 	 * @access protected
 	 */
-	function _init_caps() {
+	function _init_caps( $cap_key = '' ) {
 		global $wpdb;
-		$this->cap_key = $wpdb->prefix . 'capabilities';
+		if ( empty($cap_key) )
+			$this->cap_key = $wpdb->prefix . 'capabilities';
+		else
+			$this->cap_key = $cap_key;
 		$this->caps = &$this->{$this->cap_key};
 		if ( ! is_array( $this->caps ) )
 			$this->caps = array();