diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 0fcda3d..57fe101 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -4,8 +4,10 @@ on: push
 
 jobs:
   build:
-
-    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        os: [ubunt-lastest, macos-14]
+    runs-on: ${{matrix.os}}
     container:
           image: ghcr.io/nnpdf/lhapdf:v2.2.8
           # image: ghcr.io/catthehacker/ubuntu:full-latest
diff --git a/pywrap/pywrap.cc b/pywrap/pywrap.cc
index 39b7885..4ccb0e4 100644
--- a/pywrap/pywrap.cc
+++ b/pywrap/pywrap.cc
@@ -31,6 +31,16 @@ PYBIND11_MODULE(_core, m) {
         .def("MuDependentTermsBand", &ApproximateCoefficientFunction::MuDependentTermsBand)
         .def("fxBand", &ApproximateCoefficientFunction::fxBand);
 
+    // ApproximateCoefficientFunctionKLMV
+    py::class_<ApproximateCoefficientFunctionKLMV>(m, "ApproximateCoefficientFunctionKLMV")
+        .def(py::init<const int&, const char&, const char&, const bool&, const double&, const double&, const int&, const int&, const int&>())
+        .def("MuIndependentTerms", &ApproximateCoefficientFunctionKLMV::MuIndependentTerms)
+        .def("MuDependentTerms", &ApproximateCoefficientFunctionKLMV::MuDependentTerms)
+        .def("fx", &ApproximateCoefficientFunctionKLMV::fx)
+        .def("MuIndependentTermsBand", &ApproximateCoefficientFunctionKLMV::MuIndependentTermsBand)
+        .def("MuDependentTermsBand", &ApproximateCoefficientFunctionKLMV::MuDependentTermsBand)
+        .def("fxBand", &ApproximateCoefficientFunctionKLMV::fxBand);
+
     // AsymptoticCoefficientFunction
     py::class_<AsymptoticCoefficientFunction>(m, "AsymptoticCoefficientFunction")
         .def(py::init<const int&, const char&, const char&, const bool&, const bool&, const bool&>())
diff --git a/src/ApproximateCoefficientFunctions.cc b/src/ApproximateCoefficientFunctions.cc
index 26cd6c0..3bbc12b 100644
--- a/src/ApproximateCoefficientFunctions.cc
+++ b/src/ApproximateCoefficientFunctions.cc
@@ -28,7 +28,7 @@ double AbstractApproximate::MuIndependentTerms(double x, double m2Q2, int nf) co
 
 Value AbstractApproximate::fxBand(double x, double m2Q2, double m2mu2, int nf) const  {
     double x_max = 1. / (1. + 4 * m2Q2);
-    if (x >= x_max || x < 0)
+    if (x >= x_max || x <= 0)
         return 0;
 
     return MuIndependentTermsBand(x, m2Q2, nf) + MuDependentTerms(x, m2Q2, m2mu2, nf);
@@ -111,7 +111,7 @@ Value ApproximateCoefficientFunction::MuIndependentTermsBand(double x, double m2
     double Amax = fact * A, Amin = A / fact, Bmax = B * fact, Bmin = B / fact;
     double Cmax = (1. + var) * C, Cmin = (1. - var) * C, Dmax = (1. + var) * D, Dmin = (1. - var) * D;
 
-    double Avec[3] = { A, Amin, Amax };
+    double Avec[3] = { A, Amax, Amin };
     double Bvec[3] = { B, Bmax, Bmin };
     double Cvec[3] = { C, Cmax, Cmin };
     double Dvec[3] = { D, Dmax, Dmin };
diff --git a/src/CoefficientFunction.cc b/src/CoefficientFunction.cc
index e82adf9..59a7600 100644
--- a/src/CoefficientFunction.cc
+++ b/src/CoefficientFunction.cc
@@ -50,21 +50,7 @@ vector<double> Value::ToVect() const {
 }
 
 Value Value::operator+(const Value& rhs) const {
-    double res_central = central_ + rhs.central_;
-    double res_higher = res_central, res_lower = res_central;
-    
-    double vec_lhs[3] = {central_, higher_, lower_};
-    double vec_rhs[3] = {rhs.central_, rhs.higher_, rhs.lower_};
-
-    double tmp;
-    for (int i=0; i<3; i++) {
-        for(int j=0; j<3; j++) {
-            tmp = vec_lhs[i] + vec_rhs[j];
-            if (tmp > res_higher) res_higher = tmp;
-            if (tmp < res_lower) res_higher = tmp;
-        }
-    }
-    return Value(res_central, res_higher, res_lower);
+    return Value(central_ + rhs.central_, higher_ + rhs.higher_, lower_ + rhs.lower_);
 }
 
 // Value Value::operator-(const Value& rhs) const {