diff --git a/cpp/purify/config.in.h b/cpp/purify/config.in.h
index 57a34a3c7..d5ed42c78 100644
--- a/cpp/purify/config.in.h
+++ b/cpp/purify/config.in.h
@@ -16,6 +16,9 @@
 //! Whether PURIFY is running with mpi
 #cmakedefine PURIFY_MPI
 
+//! Whether PURIFY is running with onnxrt (onnxruntime)
+#cmakedefine PURIFY_ONNXRT
+
 //! Whether PURIFY is running with arrayfire
 #cmakedefine PURIFY_ARRAYFIRE