diff --git a/vdirsyncer/storage/base.py b/vdirsyncer/storage/base.py
index fbdab2c..b36f58c 100644
--- a/vdirsyncer/storage/base.py
+++ b/vdirsyncer/storage/base.py
@@ -5,7 +5,7 @@ import functools
 
 from .. import exceptions, sync
 from ..utils import uniq
-from ..utils.compat import with_metaclass
+from ..utils.compat import to_native, with_metaclass
 from ..utils.vobject import Item  # noqa
 
 
@@ -77,8 +77,9 @@ class Storage(with_metaclass(StorageMeta)):
         self.read_only = bool(read_only)
 
         if collection and instance_name:
-            assert isinstance(collection, str)
-            instance_name = '{}/{}'.format(instance_name, collection)
+            # XXX: PY2 hack
+            instance_name = '{}/{}'.format(instance_name,
+                                           to_native(collection, 'utf-8'))
         self.instance_name = instance_name
         self.collection = collection