diff --git a/interfaces/cython/cantera/base.pyx b/interfaces/cython/cantera/base.pyx
index dfc14c85e..d1a3021c0 100644
--- a/interfaces/cython/cantera/base.pyx
+++ b/interfaces/cython/cantera/base.pyx
@@ -70,7 +70,7 @@ cdef class _SolutionBase:
         def __get__(self):
             return list(self._selectedSpecies)
         def __set__(self, species):
-            if isinstance(species, (str, int)):
+            if isinstance(species, (str, unicode, int)):
                 species = (species,)
             self._selectedSpecies.resize(len(species))
             for i,spec in enumerate(species):
diff --git a/interfaces/cython/cantera/onedim.pyx b/interfaces/cython/cantera/onedim.pyx
index 636cd8103..b37a619da 100644
--- a/interfaces/cython/cantera/onedim.pyx
+++ b/interfaces/cython/cantera/onedim.pyx
@@ -178,7 +178,7 @@ cdef class Boundary1D(Domain1D):
         """ Species mole fractions at this boundary. """
         def __set__(self, X):
             cdef np.ndarray[np.double_t, ndim=1] data
-            if isinstance(X, str):
+            if isinstance(X, (str, unicode)):
                 self.boundary.setMoleFractions(stringify(X))
             else:
                 data = np.ascontiguousarray(X, dtype=np.double)
@@ -457,7 +457,7 @@ cdef class Sim1D:
     def _get_indices(self, dom, comp):
         idom = self.domainIndex(dom)
         dom = self.domains[idom]
-        if isinstance(comp, str):
+        if isinstance(comp, (str, unicode)):
             kcomp = dom.componentIndex(comp)
         else:
             kcomp = comp
diff --git a/interfaces/cython/cantera/reactor.pyx b/interfaces/cython/cantera/reactor.pyx
index bf2db02c8..febc42a9b 100644
--- a/interfaces/cython/cantera/reactor.pyx
+++ b/interfaces/cython/cantera/reactor.pyx
@@ -774,7 +774,7 @@ cdef class ReactorNet:
     def sensitivity(self, species, int p, int r=0):
         if isinstance(species, int):
             return self.net.sensitivity(species,p)
-        elif isinstance(species, str):
+        elif isinstance(species, (str, unicode)):
             return self.net.sensitivity(stringify(species), p, r)
 
     def sensitivities(self):
diff --git a/interfaces/cython/cantera/thermo.pyx b/interfaces/cython/cantera/thermo.pyx
index c863ab8e3..63d6991eb 100644
--- a/interfaces/cython/cantera/thermo.pyx
+++ b/interfaces/cython/cantera/thermo.pyx
@@ -146,7 +146,7 @@ cdef class ThermoPhase(_SolutionBase):
         an integer. In the latter case, the index is checked for validity and
         returned. If no such element is present, an exception is thrown.
         """
-        if isinstance(element, str):
+        if isinstance(element, (str, unicode)):
             index = self.thermo.elementIndex(stringify(element))
         elif isinstance(element, (int, float)):
             index = <int>element
@@ -191,7 +191,7 @@ cdef class ThermoPhase(_SolutionBase):
         an integer. In the latter case, the index is checked for validity and
         returned. If no such species is present, an exception is thrown.
         """
-        if isinstance(species, str):
+        if isinstance(species, (str, unicode)):
             index = self.thermo.speciesIndex(stringify(species))
         elif isinstance(species, (int, float)):
             index = <int>species
@@ -253,7 +253,7 @@ cdef class ThermoPhase(_SolutionBase):
         def __get__(self):
             return self._getArray1(thermo_getMassFractions)
         def __set__(self, Y):
-            if isinstance(Y, str):
+            if isinstance(Y, (str, unicode)):
                 self.thermo.setMassFractionsByName(stringify(Y))
             else:
                 self._setArray1(thermo_setMassFractions, Y)
@@ -272,7 +272,7 @@ cdef class ThermoPhase(_SolutionBase):
         def __get__(self):
             return self._getArray1(thermo_getMoleFractions)
         def __set__(self, X):
-            if isinstance(X, str):
+            if isinstance(X, (str, unicode)):
                 self.thermo.setMoleFractionsByName(stringify(X))
             else:
                 self._setArray1(thermo_setMoleFractions, X)