diff --git a/src/Numerics/Optimization/BaseObjectiveFunction.cs b/src/Numerics/Optimization/BaseObjectiveFunction.cs
index e85b5e7d..b8f663f3 100644
--- a/src/Numerics/Optimization/BaseObjectiveFunction.cs
+++ b/src/Numerics/Optimization/BaseObjectiveFunction.cs
@@ -1,10 +1,20 @@
-using MathNet.Numerics.LinearAlgebra;
+using System;
+using MathNet.Numerics.LinearAlgebra;
 
 namespace MathNet.Numerics.Optimization
 {
     public abstract class BaseObjectiveFunction : IObjectiveFunction
     {
-        public EvaluationStatus Status { get; protected set; }
+        [Flags]
+        enum EvaluationStatus
+        {
+            None = 0,
+            Value = 1,
+            Gradient = 2,
+            Hessian = 4
+        }
+
+        EvaluationStatus Status { get; set; }
 
         protected Vector<double> PointRaw { get; set; }
         protected double ValueRaw { get; set; }
diff --git a/src/Numerics/Optimization/IObjectiveFunction.cs b/src/Numerics/Optimization/IObjectiveFunction.cs
index bc335ded..d78bee72 100644
--- a/src/Numerics/Optimization/IObjectiveFunction.cs
+++ b/src/Numerics/Optimization/IObjectiveFunction.cs
@@ -1,17 +1,7 @@
-using System;
-using MathNet.Numerics.LinearAlgebra;
+using MathNet.Numerics.LinearAlgebra;
 
 namespace MathNet.Numerics.Optimization
 {
-    [Flags]
-    public enum EvaluationStatus
-    {
-        None = 0,
-        Value = 1,
-        Gradient = 2,
-        Hessian = 4
-    }
-
     public interface IObjectiveFunction
     {
         void EvaluateAt(Vector<double> point);