diff --git a/include/cantera/thermo/BinarySolutionTabulatedThermo.h b/include/cantera/thermo/BinarySolutionTabulatedThermo.h
index 671b22a9e..11c2e9d7f 100644
--- a/include/cantera/thermo/BinarySolutionTabulatedThermo.h
+++ b/include/cantera/thermo/BinarySolutionTabulatedThermo.h
@@ -156,7 +156,7 @@ protected:
     size_t m_kk_tab;
 
     //! Current tabulated species mole fraction
-    double m_xlast;
+    mutable double m_xlast;
 
     //! Vector for storing tabulated thermo
     vector_fp m_molefrac_tab;
@@ -164,7 +164,7 @@ protected:
     vector_fp m_entropy_tab;
 
 private:
-    void _updateThermo();
+    virtual void _updateThermo() const;
 };
 }
 
diff --git a/include/cantera/thermo/IdealSolidSolnPhase.h b/include/cantera/thermo/IdealSolidSolnPhase.h
index 05316b5c0..adf632e69 100644
--- a/include/cantera/thermo/IdealSolidSolnPhase.h
+++ b/include/cantera/thermo/IdealSolidSolnPhase.h
@@ -681,7 +681,7 @@ private:
      * the temperature has changed, the species thermo manager is called to
      * recalculate G, Cp, H, and S at the current temperature.
      */
-    void _updateThermo() const;
+    virtual void _updateThermo() const;
 
     //@}
 };
diff --git a/src/thermo/BinarySolutionTabulatedThermo.cpp b/src/thermo/BinarySolutionTabulatedThermo.cpp
index e054ce1c0..a90285795 100644
--- a/src/thermo/BinarySolutionTabulatedThermo.cpp
+++ b/src/thermo/BinarySolutionTabulatedThermo.cpp
@@ -48,7 +48,7 @@ void BinarySolutionTabulatedThermo::compositionChanged()
     _updateThermo();
 }
 
-void BinarySolutionTabulatedThermo::_updateThermo()
+void BinarySolutionTabulatedThermo::_updateThermo() const
 {
     double tnow = temperature();
     double xnow = moleFraction(m_kk_tab);