diff --git a/src/wp-includes/http.php b/src/wp-includes/http.php
index 0b4b109d9f..57746ff802 100644
--- a/src/wp-includes/http.php
+++ b/src/wp-includes/http.php
@@ -510,7 +510,7 @@ function wp_http_validate_url( $url ) {
 	if ( 80 === $port || 443 === $port || 8080 === $port )
 		return $url;
 
-	if ( $parsed_home && $same_host && $parsed_home['port'] === $port )
+	if ( $parsed_home && $same_host && isset( $parsed_home['port'] ) && $parsed_home['port'] === $port )
 		return $url;
 
 	return false;