diff --git a/src/samplefunctional.hh b/src/samplefunctional.hh
index dd7c4b8276c0992cf784723f40538803a5404d68..4186838c799ba08bbe06af1f46f8d542af073dc9 100644
--- a/src/samplefunctional.hh
+++ b/src/samplefunctional.hh
@@ -26,10 +26,10 @@ class SampleFunctional {
 
   double operator()(const SmallVector v) const {
     SmallVector y;
-    A.mv(v, y);             // y = Av
-    y /= 2;                 // y = 1/2 Av
-    y -= b;                 // y = 1/2 Av - b
-    return y * v + phi_(v); // <1/2 Av - b,v> + H(|v|)
+    A.mv(v, y);            // y = Av
+    y /= 2;                // y = 1/2 Av
+    y -= b;                // y = 1/2 Av - b
+    return y * v + phi(v); // <1/2 Av - b,v> + H(|v|)
   }
 
   void descentDirection(const SmallVector x, SmallVector &ret) const {
@@ -38,7 +38,7 @@ class SampleFunctional {
       SmallVector const d = smoothGradient(x);
 
       Interval<double> D;
-      phi_.directionalSubDiff(x, d, D);
+      phi.directionalSubDiff(x, d, D);
       double const nonlinearDecline = D[1];
       double const smoothDecline = -(d * d);
       double const combinedDecline = smoothDecline + nonlinearDecline;
@@ -82,10 +82,9 @@ class SampleFunctional {
 
   SmallMatrix A;
   SmallVector b;
+  NonlinearityType phi;
 
 private:
-  NonlinearityType phi_;
-
   // Gradient of the smooth part
   SmallVector smoothGradient(const SmallVector x) const {
     SmallVector y;
@@ -96,14 +95,14 @@ class SampleFunctional {
 
   SmallVector upperGradient(const SmallVector x) const {
     SmallVector y;
-    phi_.upperGradient(x, y);
+    phi.upperGradient(x, y);
     y += smoothGradient(x);
     return y;
   }
 
   SmallVector lowerGradient(const SmallVector x) const {
     SmallVector y;
-    phi_.lowerGradient(x, y);
+    phi.lowerGradient(x, y);
     y += smoothGradient(x);
     return y;
   }