diff --git a/src/pyAMReX.H b/src/pyAMReX.H
index d9c1a5c6..9b716590 100644
--- a/src/pyAMReX.H
+++ b/src/pyAMReX.H
@@ -6,6 +6,8 @@
  * Authors: Axel Huebl
  * License: BSD-3-Clause-LBNL
  */
+#pragma once
+
 #include <pybind11/pybind11.h>
 #include <pybind11/functional.h>
 #include <pybind11/numpy.h>