diff --git a/include/cantera/thermo/MaskellSolidSolnPhase.h b/include/cantera/thermo/MaskellSolidSolnPhase.h
index 22b2b7e1d..483d3cf8e 100644
--- a/include/cantera/thermo/MaskellSolidSolnPhase.h
+++ b/include/cantera/thermo/MaskellSolidSolnPhase.h
@@ -123,6 +123,9 @@ public:
     virtual void initThermoXML(XML_Node& phaseNode, const std::string& id);
 
     void set_h_mix(const doublereal hmix) { h_mixing = hmix; }
+
+    //! Set the product Species. Must be called after species have been added.
+    void setProductSpecies(const std::string& name);
     //@}
 
 private:
diff --git a/src/thermo/MaskellSolidSolnPhase.cpp b/src/thermo/MaskellSolidSolnPhase.cpp
index 7f58c373a..8f2a34fd5 100644
--- a/src/thermo/MaskellSolidSolnPhase.cpp
+++ b/src/thermo/MaskellSolidSolnPhase.cpp
@@ -24,8 +24,8 @@ MaskellSolidSolnPhase::MaskellSolidSolnPhase() :
     m_g0_RT(2),
     m_s0_R(2),
     h_mixing(0.0),
-    product_species_index(0),
-    reactant_species_index(1)
+    product_species_index(-1),
+    reactant_species_index(-1)
 {
 }
 
@@ -209,17 +209,9 @@ void MaskellSolidSolnPhase::initThermoXML(XML_Node& phaseNode, const std::string
         }
 
         if (thNode.hasChild("product_species")) {
-            std::string product_species_name = thNode.child("product_species").value();
-            product_species_index = static_cast<int>(speciesIndex(product_species_name));
-            if (product_species_index == -1) {
-                throw CanteraError("MaskellSolidSolnPhase::initThermoXML",
-                                   "Species " + product_species_name + " not found.");
-            }
-            if (product_species_index == 0) {
-                reactant_species_index = 1;
-            } else {
-                reactant_species_index = 0;
-            }
+            setProductSpecies(thNode.child("product_species").value());
+        } else {
+            setProductSpecies(speciesName(0)); // default
         }
     } else {
         throw CanteraError("MaskellSolidSolnPhase::initThermoXML",
@@ -236,6 +228,16 @@ void MaskellSolidSolnPhase::initThermoXML(XML_Node& phaseNode, const std::string
     VPStandardStateTP::initThermoXML(phaseNode, id_);
 }
 
+void MaskellSolidSolnPhase::setProductSpecies(const std::string& name)
+{
+    product_species_index = static_cast<int>(speciesIndex(name));
+    if (product_species_index == -1) {
+        throw CanteraError("MaskellSolidSolnPhase::setProductSpecies",
+                           "Species '{}' not found", name);
+    }
+    reactant_species_index = (product_species_index == 0) ? 1 : 0;
+}
+
 void MaskellSolidSolnPhase::_updateThermo() const
 {
     assert(m_kk == 2);
diff --git a/test/thermo/MaskellSolidSolnPhase_Test.cpp b/test/thermo/MaskellSolidSolnPhase_Test.cpp
index e56ea356e..abf592923 100644
--- a/test/thermo/MaskellSolidSolnPhase_Test.cpp
+++ b/test/thermo/MaskellSolidSolnPhase_Test.cpp
@@ -1,6 +1,9 @@
 #include "gtest/gtest.h"
 #include "cantera/thermo/MaskellSolidSolnPhase.h"
 #include "cantera/thermo/ThermoFactory.h"
+#include "cantera/thermo/PDSS_ConstVol.h"
+#include "cantera/thermo/ConstCpPoly.h"
+#include "cantera/base/stringUtils.h"
 #include <iostream>
 
 namespace Cantera
@@ -8,8 +11,6 @@ namespace Cantera
 
 class MaskellSolidSolnPhase_Test : public testing::Test
 {
-protected:
-    std::unique_ptr<ThermoPhase> test_phase;
 public:
     void initializeTestPhaseWithXML(const std::string & filename)
     {
@@ -35,6 +36,11 @@ public:
             EXPECT_NEAR(1000.+expected_result[i], chemPotentials[1], 1.e-6);
         }
     }
+
+    std::unique_ptr<ThermoPhase> test_phase;
+    const double expected_result_0[9] = {1.2338461168724738e7, 8.011774549216799e6, 4.990989640314685e6, 2.415973128783114e6, 0., -2.415973128783114e6, -4.99098964031469e6, -8.0117745492168e6, -1.2338461168724738e7};
+    const double expected_result_5000[9] = { 1.233625377465302e7, 8.00995666545047e6, 4.989677478024063e6, 2.41528026460977e6, 0., -2.415280264609771e6, -4.989677478024068e6, -8.00995666545047e6, -1.233625377465302e7 };
+    const double expected_result_minus_5000[9] = { 1.2340671035887627e7, 8.013594700219031e6, 4.992303607179179e6, 2.4166670154679064e6, 0., -2.4166670154679064e6, -4.9923036071791835e6, -8.013594700219034e6, -1.2340671035887627e7};
 };
 
 TEST_F(MaskellSolidSolnPhase_Test, construct_from_xml)
@@ -58,15 +64,12 @@ TEST_F(MaskellSolidSolnPhase_Test, chem_potentials)
     MaskellSolidSolnPhase* maskell_phase = dynamic_cast<MaskellSolidSolnPhase*>(test_phase.get());
 
     maskell_phase->set_h_mix(0.);
-    const double expected_result_0[9] = {1.2338461168724738e7, 8.011774549216799e6, 4.990989640314685e6, 2.415973128783114e6, 0., -2.415973128783114e6, -4.99098964031469e6, -8.0117745492168e6, -1.2338461168724738e7};
     check_chemPotentials(expected_result_0);
 
     maskell_phase->set_h_mix(5000.);
-    const double expected_result_5000[9] = { 1.233625377465302e7, 8.00995666545047e6, 4.989677478024063e6, 2.41528026460977e6, 0., -2.415280264609771e6, -4.989677478024068e6, -8.00995666545047e6, -1.233625377465302e7 };
     check_chemPotentials(expected_result_5000);
 
     maskell_phase->set_h_mix(-5000.);
-    const double expected_result_minus_5000[9] = { 1.2340671035887627e7, 8.013594700219031e6, 4.992303607179179e6, 2.4166670154679064e6, 0., -2.4166670154679064e6, -4.9923036071791835e6, -8.013594700219034e6, -1.2340671035887627e7};
     check_chemPotentials(expected_result_minus_5000);
 }
 
@@ -137,4 +140,47 @@ TEST_F(MaskellSolidSolnPhase_Test, activityConcentrations)
     }
 }
 
+TEST_F(MaskellSolidSolnPhase_Test, fromScratch) {
+    auto sH = make_shared<Species>("H(s)", parseCompString("H:1 He:2"));
+    double coeffs1[] = {1.0, 0.0, 0.0, 0.0};
+    sH->thermo.reset(new ConstCpPoly(250, 800, 1e5, coeffs1));
+
+    auto sHe = make_shared<Species>("He(s)", parseCompString("He:1"));
+    double coeffs2[] = {1.0, 1000.0, 0.0, 0.0};
+    sHe->thermo.reset(new ConstCpPoly(250, 800, 1e5, coeffs2));
+
+    MaskellSolidSolnPhase* p = new MaskellSolidSolnPhase();
+    test_phase.reset(p);
+
+    p->addUndefinedElements();
+    p->addSpecies(sH);
+    p->addSpecies(sHe);
+
+    std::unique_ptr<PDSS_ConstVol> ssH(new PDSS_ConstVol());
+    ssH->setMolarVolume(0.005);
+    p->installPDSS(0, std::move(ssH));
+
+    std::unique_ptr<PDSS_ConstVol> ssHe(new PDSS_ConstVol());
+    ssHe->setMolarVolume(0.01);
+    p->installPDSS(1, std::move(ssHe));
+
+    p->set_h_mix(5000);
+    p->setProductSpecies("H(s)");
+
+    p->initThermo();
+    p->setState_TPX(298, 1, "H(s):0.90   He(s):0.10");
+
+    vector_fp pmv(2);
+    p->getPartialMolarVolumes(&pmv[0]);
+    EXPECT_EQ(0.005, pmv[0]);
+    EXPECT_EQ(0.01, pmv[1]);
+
+    // Compare with XML chem_potentials test
+    p->set_h_mix(5000.);
+    check_chemPotentials(expected_result_5000);
+
+    p->set_h_mix(-5000.);
+    check_chemPotentials(expected_result_minus_5000);
+}
+
 };