diff --git a/pisi/api.py b/pisi/api.py
index a417bb9c..be2ba77e 100644
--- a/pisi/api.py
+++ b/pisi/api.py
@@ -142,7 +142,7 @@ def finalize():
 
 def list_available(repo = None):
     '''returns a set of available package names'''
-    return ctx.packagedb.list_packages(repo = repo)
+    return set(ctx.packagedb.list_packages(repo = repo))
 
 def list_upgradable():
     ignore_build = ctx.get_option('ignore_build_no')