diff --git a/src/wp-includes/http.php b/src/wp-includes/http.php
index 8dfa62cd20..d76298368f 100644
--- a/src/wp-includes/http.php
+++ b/src/wp-includes/http.php
@@ -593,7 +593,7 @@ function wp_http_validate_url( $url ) {
 	 * @param string $url           Requested URL.
 	 */
 	$allowed_ports = apply_filters( 'http_allowed_safe_ports', array( 80, 443, 8080 ), $host, $url );
-	if ( in_array( $port, $allowed_ports, true ) ) {
+	if ( is_array( $allowed_ports ) && in_array( $port, $allowed_ports, true ) ) {
 		return $url;
 	}