diff --git a/include/cantera/thermo/PDSS_ConstVol.h b/include/cantera/thermo/PDSS_ConstVol.h
index 745e853db..a61379070 100644
--- a/include/cantera/thermo/PDSS_ConstVol.h
+++ b/include/cantera/thermo/PDSS_ConstVol.h
@@ -55,6 +55,12 @@ public:
     virtual void initThermo();
     virtual void setParametersFromXML(const XML_Node& speciesNode);
 
+    //! Set the (constant) molar volume [m3/kmol] of the species. Must be called before
+    //! initThermo().
+    void setMolarVolume(double v) {
+        m_constMolarVolume = v;
+    }
+
     //@}
 
 private:
diff --git a/src/thermo/PDSS_ConstVol.cpp b/src/thermo/PDSS_ConstVol.cpp
index dbfdc7d32..22d45a946 100644
--- a/src/thermo/PDSS_ConstVol.cpp
+++ b/src/thermo/PDSS_ConstVol.cpp
@@ -34,7 +34,7 @@ void PDSS_ConstVol::setParametersFromXML(const XML_Node& speciesNode)
                            "standardState model for species isn't constant_incompressible: " + speciesNode.name());
     }
 
-    m_constMolarVolume = getFloat(*ss, "molarVolume", "toSI");
+    setMolarVolume(getFloat(*ss, "molarVolume", "toSI"));
 }
 
 void PDSS_ConstVol::initThermo()