diff --git a/src/vpp-api/python/vpp_papi/vpp_serializer.py b/src/vpp-api/python/vpp_papi/vpp_serializer.py
index a568033..f46f207 100644
--- a/src/vpp-api/python/vpp_papi/vpp_serializer.py
+++ b/src/vpp-api/python/vpp_papi/vpp_serializer.py
@@ -139,8 +139,8 @@
         self.fixed = True if num else False
         if self.fixed and not self.limit:
             raise VPPSerializerValueError(
-                "Invalid argument length for: {}, {} maximum {}".
-                format(list, len(list), self.limit))
+                "Invalid combination for: {}, {} fixed:{} limit:{}".
+                format(name, options, self.fixed, self.limit))
 
     def pack(self, list, kwargs=None):
         if not list: