diff --git a/opm/material/fluidsystems/BrineCO2FluidSystem.hpp b/opm/material/fluidsystems/BrineCO2FluidSystem.hpp
index 1d6c640a7..849e1fda1 100644
--- a/opm/material/fluidsystems/BrineCO2FluidSystem.hpp
+++ b/opm/material/fluidsystems/BrineCO2FluidSystem.hpp
@@ -45,8 +45,6 @@
 #include <opm/material/binarycoefficients/Brine_CO2.hpp>
 #include <opm/material/binarycoefficients/H2O_N2.hpp>
 
-#include <iostream>
-
 namespace Opm {
 
 /*!
@@ -485,17 +483,28 @@ private:
         Valgrind::CheckDefined(xlH2O);
         Valgrind::CheckDefined(xlCO2);
 
+        auto tostring = [](const auto& val) -> std::string
+                        {
+                            if constexpr (DenseAd::is_evaluation<LhsEval>::value) {
+                                return std::to_string(getValue(val.value()));
+                            } else {
+                                return std::to_string(val);
+                            }
+                        };
+
         if(T < 273.15) {
-            std::ostringstream oss;
-            oss << "Liquid density for Brine and CO2 is only "
-                "defined above 273.15K (is "<<T<<"K)";
-            throw NumericalProblem(oss.str());
+            const std::string msg =
+                "Liquid density for Brine and CO2 is only "
+                "defined above 273.15K (is +"
+                + tostring(T)+ "K)";
+            throw NumericalProblem(msg);
         }
         if(pl >= 2.5e8) {
-            std::ostringstream oss;
-            oss << "Liquid density for Brine and CO2 is only "
-                "defined below 250MPa (is "<<pl<<"Pa)";
-            throw NumericalProblem(oss.str());
+            const std::string msg =
+                "Liquid density for Brine and CO2 is only "
+                "defined below 250MPa (is "
+                + tostring(pl) + "Pa)";
+            throw NumericalProblem(msg);
         }
 
         const LhsEval& rho_brine = Brine::liquidDensity(T, pl);