diff --git a/rhodecode/apps/repository/utils.py b/rhodecode/apps/repository/utils.py
--- a/rhodecode/apps/repository/utils.py
+++ b/rhodecode/apps/repository/utils.py
@@ -55,7 +55,7 @@ def reviewer_as_json(user, reasons=None,
 
 def to_reviewers(e):
     if isinstance(e, (tuple, list)):
-        return map(reviewer_as_json, e)
+        return list(map(reviewer_as_json, e))
     else:
         return reviewer_as_json(e)