diff --git a/interfaces/cython/cantera/_cantera.pxd b/interfaces/cython/cantera/_cantera.pxd
index 6dbf992d551..7294e201fa9 100644
--- a/interfaces/cython/cantera/_cantera.pxd
+++ b/interfaces/cython/cantera/_cantera.pxd
@@ -55,6 +55,7 @@ cdef extern from "cantera/base/AnyMap.h" namespace "Cantera":
     cdef cppclass CxxAnyMap "Cantera::AnyMap":
         CxxAnyMap()
         CxxAnyValue& operator[](string) except +translate_exception
+        CxxAnyValue& at(string) except +translate_exception
         string keys_str()
 
     cdef cppclass CxxAnyValue "Cantera::AnyValue":
diff --git a/interfaces/cython/cantera/base.pyx b/interfaces/cython/cantera/base.pyx
index d147980dcec..2816544d9ad 100644
--- a/interfaces/cython/cantera/base.pyx
+++ b/interfaces/cython/cantera/base.pyx
@@ -122,8 +122,8 @@ cdef class _SolutionBase:
             root = AnyMapFromYamlString(stringify(source))
             self._source = 'custom YAML'
 
-        phaseNode = root[stringify("phases")].getMapWhere(stringify("name"),
-                                                          stringify(name))
+        phaseNode = root.at(stringify("phases")).getMapWhere(stringify("name"),
+                                                             stringify(name))
 
         # Thermo
         if isinstance(self, ThermoPhase):
diff --git a/interfaces/cython/cantera/test/test_thermo.py b/interfaces/cython/cantera/test/test_thermo.py
index 56a80b691f5..a59618dcd92 100644
--- a/interfaces/cython/cantera/test/test_thermo.py
+++ b/interfaces/cython/cantera/test/test_thermo.py
@@ -17,6 +17,22 @@ def setUp(self):
     def test_source(self):
         self.assertEqual(self.phase.source, 'h2o2.xml')
 
+    def test_missing_phases_key(self):
+        yaml = '''
+        species:
+        - name: H
+          composition: {H: 1}
+          thermo:
+            model: NASA7
+            temperature-ranges: [200.0, 1000.0, 6000.0]
+            data:
+            - [2.5, 0.0, 0.0, 0.0, 0.0, 2.547366e+04, -0.44668285]
+            - [2.5, 0.0, 0.0, 0.0, 0.0, 2.547366e+04, -0.44668285]
+            note: L6/94
+        '''
+        with self.assertRaisesRegex(ct.CanteraError, "Key 'phases' not found"):
+            _ = ct.Solution(yaml=yaml)
+
     def test_base_attributes(self):
         self.assertIsInstance(self.phase.name, str)
         self.assertIsInstance(self.phase.phase_of_matter, str)