diff --git a/Cantera/src/thermo/WaterSSTP.cpp b/Cantera/src/thermo/WaterSSTP.cpp
index 2d6ee9d0e..29130b8a9 100644
--- a/Cantera/src/thermo/WaterSSTP.cpp
+++ b/Cantera/src/thermo/WaterSSTP.cpp
@@ -16,6 +16,7 @@
 #include "WaterSSTP.h"
 #include "WaterPropsIAPWS.h"
 #include "importCTML.h"
+#include <math.h>
 
 namespace Cantera {
   /**
@@ -517,11 +518,11 @@ namespace Cantera {
      
 
   // saturation pressure
-  doublereal WaterSSTP::satPressure(doublereal t){
+  doublereal WaterSSTP::satPressure(doublereal t) const {
+    doublereal tsave = temperature();
+    doublereal dsave = density();
     doublereal pp = m_sub->psat(t);
-    double dens = density();
-    setTemperature(t);
-    setDensity(dens);
+    m_sub->setState(tsave, dsave);
     return pp;
   }
 
diff --git a/Cantera/src/thermo/WaterSSTP.h b/Cantera/src/thermo/WaterSSTP.h
index d4567e2fa..077792b81 100644
--- a/Cantera/src/thermo/WaterSSTP.h
+++ b/Cantera/src/thermo/WaterSSTP.h
@@ -374,7 +374,7 @@ namespace Cantera {
     /*!
      * @param t Temperature (kelvin)
      */
-    virtual doublereal satPressure(doublereal t);
+    virtual doublereal satPressure(doublereal t) const;
     
     //! Return the fraction of vapor at the current conditions
     /*!