diff --git a/Grid/qcd/action/fermion/FermionOperator.h b/Grid/qcd/action/fermion/FermionOperator.h
index 7c64ea35..ac311d88 100644
--- a/Grid/qcd/action/fermion/FermionOperator.h
+++ b/Grid/qcd/action/fermion/FermionOperator.h
@@ -28,8 +28,7 @@ Author: Vera Guelpers <V.M.Guelpers@soton.ac.uk>
     See the full license in the file "LICENSE" in the top level distribution directory
 *************************************************************************************/
 /*  END LEGAL */
-#ifndef  GRID_QCD_FERMION_OPERATOR_H
-#define  GRID_QCD_FERMION_OPERATOR_H
+#pragma once
 
 NAMESPACE_BEGIN(Grid);
 
@@ -172,4 +171,3 @@ public:
 
 NAMESPACE_END(Grid);
 
-#endif