diff --git a/Cantera/src/thermo/WaterSSTP.cpp b/Cantera/src/thermo/WaterSSTP.cpp
index b27f643a7..99dae3074 100644
--- a/Cantera/src/thermo/WaterSSTP.cpp
+++ b/Cantera/src/thermo/WaterSSTP.cpp
@@ -486,6 +486,22 @@ namespace Cantera {
     setDensity(dd);
   }
   
+  // Returns  the isothermal compressibility. Units: 1/Pa.
+  /*
+   * The isothermal compressibility is defined as
+   * \f[
+   * \kappa_T = -\frac{1}{v}\left(\frac{\partial v}{\partial P}\right)_T
+   * \f]
+   *  or
+   * \f[
+   * \kappa_T = \frac{1}{\rho}\left(\frac{\partial \rho}{\partial P}\right)_T
+   * \f]
+   */
+  doublereal WaterSSTP::isothermalCompressibility() const {
+    doublereal val = m_sub->isothermalCompressibility();
+    return val;
+  }
+
   // Return the volumetric thermal expansion coefficient. Units: 1/K.
   /*
    * The thermal expansion coefficient is defined as
diff --git a/Cantera/src/thermo/WaterSSTP.h b/Cantera/src/thermo/WaterSSTP.h
index 07c1e4db5..3e05623b4 100644
--- a/Cantera/src/thermo/WaterSSTP.h
+++ b/Cantera/src/thermo/WaterSSTP.h
@@ -186,6 +186,19 @@ namespace Cantera {
     virtual doublereal pressure() const;
     virtual void setPressure(doublereal p);
 
+    //! Returns  the isothermal compressibility. Units: 1/Pa.
+    /*!
+     * The isothermal compressibility is defined as
+     * \f[
+     * \kappa_T = -\frac{1}{v}\left(\frac{\partial v}{\partial P}\right)_T
+     * \f]
+     *  or
+     * \f[
+     * \kappa_T = \frac{1}{\rho}\left(\frac{\partial \rho}{\partial P}\right)_T
+     * \f]
+     */
+    virtual doublereal isothermalCompressibility() const;
+
     //! Return the volumetric thermal expansion coefficient. Units: 1/K.
     /*!
      * The thermal expansion coefficient is defined as