diff --git a/lib/algorithms/LinearOperator.h b/lib/algorithms/LinearOperator.h
index 167213ec..cb6240ba 100644
--- a/lib/algorithms/LinearOperator.h
+++ b/lib/algorithms/LinearOperator.h
@@ -106,6 +106,10 @@ namespace Grid {
     public:
       virtual void operator() (LinearOperatorBase<Field> &Linop, const Field &in, Field &out) = 0;
     };
+    template<class Field> class HermitianOperatorFunction {
+    public:
+      virtual void operator() (HermitianOperatorBase<Field> &Linop, const Field &in, Field &out) = 0;
+    };
 
     // FIXME : To think about