diff --git a/include/cantera/thermo/LatticePhase.h b/include/cantera/thermo/LatticePhase.h
index 8d75c3379..33b6ab544 100644
--- a/include/cantera/thermo/LatticePhase.h
+++ b/include/cantera/thermo/LatticePhase.h
@@ -216,7 +216,6 @@ namespace Cantera
  *     <reactionArray datasrc="#reaction_data"/>
  *     <thermo model="Lattice">
  *       <site_density> 73.159 </site_density>
- *       <vacancy_species>  Vac_O </vacancy_species>
  *     </thermo>
  *     <kinetics model="BulkKinetics"/>
  *     <transport model="None"/>
@@ -649,7 +648,6 @@ public:
      * <phase id="O_lattice_SiO2" >
      *   <thermo model="Lattice">
      *     <site_density units="kmol/m^3"> 73.159 </site_density>
-     *     <vacancy_species> "O_vacancy"  </vacancy_species>
      *   </thermo>
      * </phase>
      * @endcode
@@ -685,12 +683,6 @@ protected:
     //! temperature
     mutable vector_fp m_s0_R;
 
-    //! String name for the species which represents a vacancy in the lattice
-    /*!
-     *  This string is currently unused
-     */
-    std::string m_vacancy;
-
     //! Vector of molar volumes for each species in the solution
     /**
      * Species molar volumes \f$ m^3 kmol^-1 \f$
diff --git a/interfaces/cython/cantera/ctml_writer.py b/interfaces/cython/cantera/ctml_writer.py
index 64a814117..83f095d92 100644
--- a/interfaces/cython/cantera/ctml_writer.py
+++ b/interfaces/cython/cantera/ctml_writer.py
@@ -2154,13 +2154,11 @@ class lattice(phase):
                  transport = 'None',
                  initial_state = None,
                  options = [],
-                 site_density = None,
-                 vacancy_species = ''):
+                 site_density = None):
         phase.__init__(self, name, 3, elements, species, note, 'none',
                         initial_state, options)
         self._tr = transport
         self._n = site_density
-        self._vac = vacancy_species
         self._species = species
         if name == '':
             raise CTI_Error('sublattice name must be specified')
@@ -2177,8 +2175,6 @@ class lattice(phase):
         e = ph.child('thermo')
         e['model'] = 'Lattice'
         addFloat(e, 'site_density', self._n, defunits = _umol+'/'+_ulen+'3')
-        if self._vac:
-            e.addChild('vacancy_species',self._vac)
         if self._tr:
             t = ph.addChild('transport')
             t['model'] = self._tr
diff --git a/src/thermo/LatticePhase.cpp b/src/thermo/LatticePhase.cpp
index baeb4947a..4434232f1 100644
--- a/src/thermo/LatticePhase.cpp
+++ b/src/thermo/LatticePhase.cpp
@@ -311,7 +311,6 @@ void LatticePhase::setParametersFromXML(const XML_Node& eosdata)
 {
     eosdata._require("model", "Lattice");
     m_site_density = getFloat(eosdata, "site_density", "toSI");
-    m_vacancy = getChildValue(eosdata, "vacancy_species");
 }
 
 }
diff --git a/test_problems/VCSnonideal/LatticeSolid_LiSi/Li7Si3_ls.xml b/test_problems/VCSnonideal/LatticeSolid_LiSi/Li7Si3_ls.xml
index bfecff5ac..8b3021dd4 100644
--- a/test_problems/VCSnonideal/LatticeSolid_LiSi/Li7Si3_ls.xml
+++ b/test_problems/VCSnonideal/LatticeSolid_LiSi/Li7Si3_ls.xml
@@ -35,7 +35,6 @@
          <speciesArray datasrc="#species_LiSi(S)"> Li(i) V(i) </speciesArray>
          <thermo model="Lattice">
            <site_density units="gmol/cm3"> 1.046344E-2 </site_density>
-           <vacancy_species> V(i) </vacancy_species>
          </thermo>
          <transport model="None"/>
          <kinetics model="none"/>