diff --git a/dumux/material/components/co2.hh b/dumux/material/components/co2.hh
index d8e303f6180c8a47d085c58e45e2b560d8b2a451..9bc5fd360e474f5c5664d3cf8499c744f3946fb6 100644
--- a/dumux/material/components/co2.hh
+++ b/dumux/material/components/co2.hh
@@ -119,6 +119,12 @@ public:
     static Scalar maxTabulatedTemperature()
     { return CO2Tables::tabulatedEnthalpy.maxTemp(); /* [K] */ }
 
+    /*!
+     * \brief Returns true if the gas phase is assumed to be ideal
+     */
+    static constexpr bool gasIsIdeal()
+    { return false; }
+
     /*!
      * \brief The vapor pressure in \f$\mathrm{[Pa]}\f$ of pure CO2
      *        at a given temperature.