diff --git a/opm/material/fluidstates/FluidStateCompositionModules.hpp b/opm/material/fluidstates/FluidStateCompositionModules.hpp
index a85d16356..e384612a5 100644
--- a/opm/material/fluidstates/FluidStateCompositionModules.hpp
+++ b/opm/material/fluidstates/FluidStateCompositionModules.hpp
@@ -34,6 +34,7 @@
 #include <opm/material/common/Exceptions.hpp>
 
 #include <algorithm>
+#include <array>
 #include <cmath>
 
 namespace Opm {
@@ -165,9 +166,9 @@ protected:
     const Implementation& asImp_() const
     { return *static_cast<const Implementation*>(this); }
 
-    Scalar moleFraction_[numPhases][numComponents];
-    Scalar averageMolarMass_[numPhases];
-    Scalar sumMoleFractions_[numPhases];
+    std::array<std::array<Scalar,numComponents>,numPhases> moleFraction_;
+    std::array<Scalar,numPhases> averageMolarMass_;
+    std::array<Scalar,numPhases> sumMoleFractions_;
 };
 
 /*!