diff --git a/parser/common/parser_types.cc b/parser/common/parser_types.cc
index b53d37a..6596efb 100644
--- a/parser/common/parser_types.cc
+++ b/parser/common/parser_types.cc
@@ -432,6 +432,9 @@ const char *SIGMOIDGRAD = "SigmoidGrad";
 
 const char *TRANSSHAPE = "TransShape";
 
+// Onnx model output operator
+const char *_RETVAL = "_Retval";
+
 // Horovod operator
 const char *HVDCALLBACKALLREDUCE = "HorovodAllreduce";
 const char *HVDCALLBACKALLGATHER = "HorovodAllgather";