diff --git a/interfaces/cython/cantera/_cantera.pxd b/interfaces/cython/cantera/_cantera.pxd
index 7294e201fa9..dde5d9db806 100644
--- a/interfaces/cython/cantera/_cantera.pxd
+++ b/interfaces/cython/cantera/_cantera.pxd
@@ -54,7 +54,6 @@ 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()
 
diff --git a/interfaces/cython/cantera/reaction.pyx b/interfaces/cython/cantera/reaction.pyx
index 0f7bfa6de5b..3009ecc4c85 100644
--- a/interfaces/cython/cantera/reaction.pyx
+++ b/interfaces/cython/cantera/reaction.pyx
@@ -141,7 +141,7 @@ cdef class Reaction:
             if kinetics is None:
                 raise ValueError("A Kinetics object is required.")
             root = AnyMapFromYamlFile(stringify(filename))
-            cxx_reactions = CxxGetReactions(root[stringify(section)],
+            cxx_reactions = CxxGetReactions(root.at(stringify(section)),
                                             deref(kinetics.kinetics))
         else:
             cxx_reactions = CxxGetReactions(deref(CxxGetXmlFile(stringify(filename))))
@@ -184,7 +184,7 @@ cdef class Reaction:
         YAML string.
         """
         root = AnyMapFromYamlString(stringify(text))
-        cxx_reactions = CxxGetReactions(root[stringify("items")],
+        cxx_reactions = CxxGetReactions(root.at(stringify("items")),
                                         deref(kinetics.kinetics))
         return [wrapReaction(r) for r in cxx_reactions]
 
diff --git a/interfaces/cython/cantera/thermo.pyx b/interfaces/cython/cantera/thermo.pyx
index 9aac207fc04..57d9459ba5d 100644
--- a/interfaces/cython/cantera/thermo.pyx
+++ b/interfaces/cython/cantera/thermo.pyx
@@ -138,7 +138,7 @@ cdef class Species:
         """
         if filename.lower().split('.')[-1] in ('yml', 'yaml'):
             root = AnyMapFromYamlFile(stringify(filename))
-            cxx_species = CxxGetSpecies(root[stringify(section)])
+            cxx_species = CxxGetSpecies(root.at(stringify(section)))
         else:
             cxx_species = CxxGetSpecies(deref(CxxGetXmlFile(stringify(filename))))
 
@@ -201,7 +201,7 @@ cdef class Species:
 
         # ``items`` is the pseudo-key used to access a list when it is at the
         # top level of a YAML document
-        cxx_species = CxxGetSpecies(root[stringify(section or "items")])
+        cxx_species = CxxGetSpecies(root.at(stringify(section or "items")))
         species = []
         for a in cxx_species:
             b = Species(init=False)