diff --git a/kraken/lib/vgsl.py b/kraken/lib/vgsl.py
index 745dda816..85e04ea47 100644
--- a/kraken/lib/vgsl.py
+++ b/kraken/lib/vgsl.py
@@ -411,7 +411,7 @@ def _serialize_layer(net, input, net_builder):
             mlmodel.short_description = 'kraken model'
             mlmodel.user_defined_metadata['vgsl'] = '[' + ' '.join(self.named_spec) + ']'
             if self.codec:
-                mlmodel.user_defined_metadata['codec'] = json.dumps({'type': 'SentencePiece', 'spp': self.spp.serialized_model_proto()})
+                mlmodel.user_defined_metadata['codec'] = json.dumps({'type': 'SentencePiece', 'spp': self.codec.spp.serialized_model_proto()})
             if self.user_metadata:
                 mlmodel.user_defined_metadata['kraken_meta'] = json.dumps(self.user_metadata)
             if self.aux_layers: