diff --git a/include/Ancillaries.h b/include/Ancillaries.h
index 3d0d8734..9c04d752 100644
--- a/include/Ancillaries.h
+++ b/include/Ancillaries.h
@@ -82,15 +82,21 @@ class SaturationAncillaryFunction
 private:
     Eigen::MatrixXd num_coeffs, ///< Coefficients for numerator in rational polynomial 
                     den_coeffs; ///< Coefficients for denominator in rational polynomial
-    std::vector<double> n, t, s;
-    bool using_tau_r;
-    CoolPropDbl Tmax, Tmin, reducing_value, T_r, max_abs_error;
+    std::vector<double> n, t, s; // For TYPE_NOT_EXPONENTIAL & TYPE_EXPONENTIAL
+    union{
+        CoolPropDbl max_abs_error; // For TYPE_RATIONAL_POLYNOMIAL
+        struct{                    // For TYPE_NOT_EXPONENTIAL & TYPE_EXPONENTIAL
+            bool using_tau_r;
+            CoolPropDbl reducing_value, T_r;
+            std::size_t N;
+        };
+    };
+    CoolPropDbl Tmax, Tmin;
     enum ancillaryfunctiontypes{TYPE_NOT_SET = 0, 
                                 TYPE_NOT_EXPONENTIAL, 
                                 TYPE_EXPONENTIAL, 
                                 TYPE_RATIONAL_POLYNOMIAL};
     ancillaryfunctiontypes type;
-    std::size_t N;
 public:
 
     SaturationAncillaryFunction(){type = TYPE_NOT_SET;};
diff --git a/src/Backends/Helmholtz/Fluids/Ancillaries.cpp b/src/Backends/Helmholtz/Fluids/Ancillaries.cpp
index ccc88af0..a3231d99 100644
--- a/src/Backends/Helmholtz/Fluids/Ancillaries.cpp
+++ b/src/Backends/Helmholtz/Fluids/Ancillaries.cpp
@@ -16,6 +16,7 @@ SaturationAncillaryFunction::SaturationAncillaryFunction(rapidjson::Value &json_
     std::string type = cpjson::get_string(json_code,"type");
     if (!type.compare("rational_polynomial"))
     {
+        this->type = TYPE_RATIONAL_POLYNOMIAL;
         num_coeffs = vec_to_eigen(cpjson::get_double_array(json_code["A"]));
         den_coeffs = vec_to_eigen(cpjson::get_double_array(json_code["B"]));
         max_abs_error = cpjson::get_double(json_code,"max_abs_error");
@@ -30,7 +31,13 @@ SaturationAncillaryFunction::SaturationAncillaryFunction(rapidjson::Value &json_
     }
     else
     {
+        if (!type.compare("rhoLnoexp"))
+            this->type = TYPE_NOT_EXPONENTIAL;
+        else
+            this->type = TYPE_EXPONENTIAL;
         n = cpjson::get_double_array(json_code["n"]);
+        N = n.size();
+        s = n;
         t = cpjson::get_double_array(json_code["t"]);
         Tmin = cpjson::get_double(json_code,"Tmin");
         Tmax = cpjson::get_double(json_code,"Tmax");
@@ -39,14 +46,6 @@ SaturationAncillaryFunction::SaturationAncillaryFunction(rapidjson::Value &json_
         T_r = cpjson::get_double(json_code,"T_r");    
     }   
     
-    if (!type.compare("rational_polynomial"))
-        this->type = TYPE_RATIONAL_POLYNOMIAL;
-    else if (!type.compare("rhoLnoexp"))
-        this->type = TYPE_NOT_EXPONENTIAL;
-    else
-        this->type = TYPE_EXPONENTIAL;
-    this->N = n.size();
-    s = n;
 };
     
 double SaturationAncillaryFunction::evaluate(double T)