diff --git a/recipes/recipe_modules/gsutil/api.py b/recipes/recipe_modules/gsutil/api.py
index c4f58b2b47..152be03827 100644
--- a/recipes/recipe_modules/gsutil/api.py
+++ b/recipes/recipe_modules/gsutil/api.py
@@ -162,7 +162,7 @@ class GSUtilApi(recipe_api.RecipeApi):
   def _generate_metadata_args(self, metadata):
     result = []
     if metadata:
-      for k, v in sorted(metadata.items(), key=lambda (k, _): k):
+      for k, v in sorted(metadata.items(), key=lambda k: k[0]):
         field = self._get_metadata_field(k)
         param = (field) if v is None else ('%s:%s' % (field, v))
         result += ['-h', param]