diff --git a/Reconstruction/LwtnnUtils/LwtnnUtils/FastGraph.h b/Reconstruction/LwtnnUtils/LwtnnUtils/FastGraph.h
index 59ae7c0779e8d1c35a85d7fa875f36f98ec071ec..042e0b15df9f6fe4de4e8ea3b5fc24b9fb59e6ec 100644
--- a/Reconstruction/LwtnnUtils/LwtnnUtils/FastGraph.h
+++ b/Reconstruction/LwtnnUtils/LwtnnUtils/FastGraph.h
@@ -23,7 +23,7 @@ namespace lwt::atlas {
 
   class FastInputPreprocessor;
   class FastInputVectorPreprocessor;
-  class InputOrder;
+  struct InputOrder;
 
   struct SourceIndices
   {