diff --git a/classes/gpm.php b/classes/gpm.php
index 1a46798f..3cdcd89d 100644
--- a/classes/gpm.php
+++ b/classes/gpm.php
@@ -154,7 +154,7 @@ class Gpm
 
         $filename = $package->slug . basename($package->zipball_url);
 
-        file_put_contents($cache_dir . DS . $filename, $contents);
+        file_put_contents($cache_dir . DS . $filename . '.zip', $contents);
 
         return $cache_dir . DS . $filename;
     }