diff --git a/wp-includes/user.php b/wp-includes/user.php
index aa225a6718..0bfc9e5fc4 100644
--- a/wp-includes/user.php
+++ b/wp-includes/user.php
@@ -27,6 +27,8 @@
  */
 function wp_signon( $credentials = array(), $secure_cookie = '' ) {
 	if ( empty($credentials) ) {
+		$credentials = array(); // Back-compat for plugins passing an empty string.
+
 		if ( ! empty($_POST['log']) )
 			$credentials['user_login'] = $_POST['log'];
 		if ( ! empty($_POST['pwd']) )
diff --git a/wp-includes/version.php b/wp-includes/version.php
index d16f12355a..c3d88e73a1 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.6-alpha-37696';
+$wp_version = '4.6-alpha-37697';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.
diff --git a/wp-login.php b/wp-login.php
index 9a8a059c5e..46f1507d85 100644
--- a/wp-login.php
+++ b/wp-login.php
@@ -790,7 +790,7 @@ default:
 
 	$reauth = empty($_REQUEST['reauth']) ? false : true;
 
-	$user = wp_signon( '', $secure_cookie );
+	$user = wp_signon( array(), $secure_cookie );
 
 	if ( empty( $_COOKIE[ LOGGED_IN_COOKIE ] ) ) {
 		if ( headers_sent() ) {