diff --git a/lib/qcd/action/fermion/FermionOperator.h b/lib/qcd/action/fermion/FermionOperator.h
index daee2e5b..742c6e08 100644
--- a/lib/qcd/action/fermion/FermionOperator.h
+++ b/lib/qcd/action/fermion/FermionOperator.h
@@ -92,15 +92,16 @@ namespace Grid {
       virtual void  Mdir   (const FermionField &in, FermionField &out,int dir,int disp)=0;   // case by case Wilson, Clover, Cayley, ContFrac, PartFrac
 
 
-      virtual void  MomentumSpacePropagator(FermionField &out,const FermionField &in) { assert(0);};
-      virtual void  FreePropagator(const FermionField &in,FermionField &out) { 
+      virtual void  MomentumSpacePropagator(FermionField &out,const FermionField &in,RealD _m) { assert(0);};
+
+      virtual void  FreePropagator(const FermionField &in,FermionField &out,RealD mass) { 
 	FFT theFFT((GridCartesian *) in._grid);
 
 	FermionField in_k(in._grid);
 	FermionField prop_k(in._grid);
 
 	theFFT.FFT_all_dim(in_k,in,FFT::forward);
-        this->MomentumSpacePropagator(prop_k,in_k);
+        this->MomentumSpacePropagator(prop_k,in_k,mass);
 	theFFT.FFT_all_dim(out,prop_k,FFT::backward);
       };