diff --git a/asu/api.py b/asu/api.py
index 02bb89af..01dc04c0 100644
--- a/asu/api.py
+++ b/asu/api.py
@@ -84,7 +84,7 @@ def validate_packages(req):
         else:
             tr.add(p)
 
-    req["packages"] = list(map(lambda x: remove_prefix(x, "+"), sorted(tr)))
+    req["packages"] = set(map(lambda x: remove_prefix(x, "+"), sorted(tr)))
 
     # store request packages temporary in Redis and create a diff
     temp = str(uuid4())