diff --git a/createrepo/__init__.py b/createrepo/__init__.py

index b1875f6..85f2a3d 100644

--- a/createrepo/__init__.py

+++ b/createrepo/__init__.py

@@ -400,7 +400,9 @@ class MetaDataGenerator:

         if self.conf.update:

             self._setup_old_metadata_lookup()

         # rpms we're going to be dealing with

-        if self.conf.pkglist:

+        if isinstance(self.conf.pkglist, MetaSack):

+            packages = self.conf.pkglist

+        elif self.conf.pkglist:

             packages = []

             for pkg in self.conf.pkglist:

                 if '://' in pkg: # remote