diff --git a/src/Composer/Downloader/ZipDownloader.php b/src/Composer/Downloader/ZipDownloader.php
index b3685268b..09c32ab8a 100644
--- a/src/Composer/Downloader/ZipDownloader.php
+++ b/src/Composer/Downloader/ZipDownloader.php
@@ -29,7 +29,7 @@ use ZipArchive;
  */
 class ZipDownloader extends ArchiveDownloader
 {
-    private static $hasSystemUnzip;
+    protected static $hasSystemUnzip;
     private static $hasZipArchive;
     private static $isWindows;