diff --git a/src/wp-includes/wp-db.php b/src/wp-includes/wp-db.php
index 667ee3b25a..4bba086d3f 100644
--- a/src/wp-includes/wp-db.php
+++ b/src/wp-includes/wp-db.php
@@ -1327,6 +1327,10 @@ class wpdb {
 			} else {
 				@mysqli_real_connect( $this->dbh, $host, $this->dbuser, $this->dbpassword, null, $port, $socket, $client_flags );
 			}
+
+			if ( $this->dbh->connect_errno ) {
+				$this->dbh = null;
+			}
 		} else {
 			if ( WP_DEBUG ) {
 				$this->dbh = mysql_connect( $this->dbhost, $this->dbuser, $this->dbpassword, $new_link, $client_flags );