Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 28563)
+++ wp-includes/pluggable.php	(working copy)
@@ -1605,27 +1605,30 @@
  * @param string $plaintext_pass Optional. The user's plaintext password. Default empty.
  */
 function wp_new_user_notification($user_id, $plaintext_pass = '') {
-	$user = get_userdata( $user_id );
+	if( is_multisite() ) {
+		wpmu_welcome_user_notification( $user_id, $plaintext_pass );
+	} else {
+		$user = get_userdata( $user_id );
 
-	// The blogname option is escaped with esc_html on the way into the database in sanitize_option
-	// we want to reverse this for the plain text arena of emails.
-	$blogname = wp_specialchars_decode(get_option('blogname'), ENT_QUOTES);
+		// The blogname option is escaped with esc_html on the way into the database in sanitize_option
+		// we want to reverse this for the plain text arena of emails.
+		$blogname = wp_specialchars_decode(get_option('blogname'), ENT_QUOTES);
 
-	$message  = sprintf(__('New user registration on your site %s:'), $blogname) . "\r\n\r\n";
-	$message .= sprintf(__('Username: %s'), $user->user_login) . "\r\n\r\n";
-	$message .= sprintf(__('E-mail: %s'), $user->user_email) . "\r\n";
+		$message  = sprintf(__('New user registration on your site %s:'), $blogname) . "\r\n\r\n";
+		$message .= sprintf(__('Username: %s'), $user->user_login) . "\r\n\r\n";
+		$message .= sprintf(__('E-mail: %s'), $user->user_email) . "\r\n";
 
-	@wp_mail(get_option('admin_email'), sprintf(__('[%s] New User Registration'), $blogname), $message);
+		@wp_mail(get_option('admin_email'), sprintf(__('[%s] New User Registration'), $blogname), $message);
 
-	if ( empty($plaintext_pass) )
-		return;
+		if ( empty($plaintext_pass) )
+			return;
 
-	$message  = sprintf(__('Username: %s'), $user->user_login) . "\r\n";
-	$message .= sprintf(__('Password: %s'), $plaintext_pass) . "\r\n";
-	$message .= wp_login_url() . "\r\n";
+		$message  = sprintf(__('Username: %s'), $user->user_login) . "\r\n";
+		$message .= sprintf(__('Password: %s'), $plaintext_pass) . "\r\n";
+		$message .= wp_login_url() . "\r\n";
 
-	wp_mail($user->user_email, sprintf(__('[%s] Your username and password'), $blogname), $message);
-
+		wp_mail($user->user_email, sprintf(__('[%s] Your username and password'), $blogname), $message);
+	}
 }
 endif;