diff --git a/tests/phpunit/tests/functions/doEnclose.php b/tests/phpunit/tests/functions/doEnclose.php
index 30a8e73dac..5c8a42089f 100644
--- a/tests/phpunit/tests/functions/doEnclose.php
+++ b/tests/phpunit/tests/functions/doEnclose.php
@@ -280,7 +280,7 @@ class Tests_Functions_DoEnclose extends WP_UnitTestCase {
 
 		$path = parse_url( $url, PHP_URL_PATH );
 
-		if ( null !== $path ) {
+		if ( is_string( $path ) ) {
 			$extension = pathinfo( $path, PATHINFO_EXTENSION );
 			if ( isset( $fake_headers[ $extension ] ) ) {
 				return $fake_headers[ $extension ];