--- a/testing/mozharness/mozharness/base/script.py
+++ b/testing/mozharness/mozharness/base/script.py
@@ -624,16 +624,19 @@ class ScriptMixin(PlatformMixin):
                 },
                 'application/x-tar': {
                     'function': self.deflate,
                     'kwargs': {'mode': 'r'},
                 },
                 'application/zip': {
                     'function': self.unzip,
                 },
+                'application/x-zip-compressed': {
+                    'function': self.unzip,
+                },
             }
 
             filename = url.split('/')[-1]
             # XXX: bz2/gz instead of tar.{bz2/gz}
             extension = filename[filename.rfind('.')+1:]
             mimetype = EXTENSION_TO_MIMETYPE[extension]
             self.debug('Mimetype: {}'.format(mimetype))