diff --git a/src/mlpack/methods/decision_tree/mse_gain.hpp b/src/mlpack/methods/decision_tree/mse_gain.hpp
index 5cc8876625..8f46a9bf11 100644
--- a/src/mlpack/methods/decision_tree/mse_gain.hpp
+++ b/src/mlpack/methods/decision_tree/mse_gain.hpp
@@ -41,10 +41,10 @@ class MSEGain
    * @param end End index.
    */
   template<bool UseWeights, typename VecType, typename WeightVecType>
-  double Evaluate(const VecType& values,
-                  const WeightVecType& weights,
-                  const size_t begin,
-                  const size_t end)
+  static double Evaluate(const VecType& values,
+                         const WeightVecType& weights,
+                         const size_t begin,
+                         const size_t end)
   {
     double mse = 0.0;
 
@@ -85,8 +85,8 @@ class MSEGain
    * @param weights Weights associated to each value.
    */
   template<bool UseWeights, typename VecType, typename WeightVecType>
-  double Evaluate(const VecType& values,
-                  const WeightVecType& weights)
+  static double Evaluate(const VecType& values,
+                         const WeightVecType& weights)
   {
     // Corner case: if there are no elements, the impurity is zero.
     if (values.n_elem == 0)
diff --git a/src/mlpack/tests/decision_tree_regressor_test.cpp b/src/mlpack/tests/decision_tree_regressor_test.cpp
index ce32f90ed8..df810b0f36 100644
--- a/src/mlpack/tests/decision_tree_regressor_test.cpp
+++ b/src/mlpack/tests/decision_tree_regressor_test.cpp
@@ -77,8 +77,8 @@ TEST_CASE("MSEGainPerfectTest", "[DecisionTreeRegressorTest]")
   arma::rowvec responses;
   responses.ones(10);
 
-  MSEGain f;
-  REQUIRE(f.Evaluate<false>(responses, weights) == Approx(0.0).margin(1e-5));
+  REQUIRE(MSEGain::Evaluate<false>(responses, weights) ==
+          Approx(0.0).margin(1e-5));
 }
 
 /**
@@ -89,9 +89,10 @@ TEST_CASE("MSEGainEmptyTest", "[DecisionTreeRegressorTest]")
   arma::rowvec weights = arma::ones<arma::rowvec>(10);
   arma::rowvec responses;
 
-  MSEGain f;
-  REQUIRE(f.Evaluate<false>(responses, weights) == Approx(0.0).margin(1e-5));
-  REQUIRE(f.Evaluate<true>(responses, weights) == Approx(0.0).margin(1e-5));
+  REQUIRE(MSEGain::Evaluate<false>(responses, weights) ==
+          Approx(0.0).margin(1e-5));
+  REQUIRE(MSEGain::Evaluate<true>(responses, weights) ==
+          Approx(0.0).margin(1e-5));
 }
 
 /**
@@ -107,9 +108,9 @@ TEST_CASE("MSEGainHandCalculation", "[DecisionTreeRegressorTest]")
   const double gain = -27.08999;
   const double weightedGain = -27.53960;
 
-  MSEGain f;
-  REQUIRE(f.Evaluate<false>(responses, weights) == Approx(gain).margin(1e-5));
-  REQUIRE(f.Evaluate<true>(responses, weights) ==
+  REQUIRE(MSEGain::Evaluate<false>(responses, weights) ==
+          Approx(gain).margin(1e-5));
+  REQUIRE(MSEGain::Evaluate<true>(responses, weights) ==
           Approx(weightedGain).margin(1e-5));
 }
 
@@ -123,7 +124,7 @@ TEST_CASE("MADGainPerfectTest", "[DecisionTreeRegressorTest]")
   responses.ones(10);
 
   REQUIRE(MADGain::Evaluate<false>(responses, weights) ==
-      Approx(0.0).margin(1e-5));
+          Approx(0.0).margin(1e-5));
 }
 
 /**
@@ -156,9 +157,9 @@ TEST_CASE("MADGainEmptyTest", "[DecisionTreeRegressorTest]")
   arma::rowvec responses;
 
   REQUIRE(MADGain::Evaluate<false>(responses, weights) ==
-      Approx(0.0).margin(1e-5));
+          Approx(0.0).margin(1e-5));
   REQUIRE(MADGain::Evaluate<true>(responses, weights) ==
-      Approx(0.0).margin(1e-5));
+          Approx(0.0).margin(1e-5));
 }
 
 /**
@@ -175,7 +176,7 @@ TEST_CASE("MADGainHandCalculation", "[DecisionTreeRegressorTest]")
   const double weightedGain = -3.8592;
 
   REQUIRE(MADGain::Evaluate<false>(responses, weights) ==
-      Approx(gain).margin(1e-5));
+          Approx(gain).margin(1e-5));
   REQUIRE(MADGain::Evaluate<true>(responses, weights) ==
           Approx(weightedGain).margin(1e-5));
 }