diff --git a/cmd2/command_definition.py b/cmd2/command_definition.py
index 9f713d83..1c1ff0cf 100644
--- a/cmd2/command_definition.py
+++ b/cmd2/command_definition.py
@@ -92,10 +92,31 @@ class CommandSet(object):
     """
 
     def __init__(self) -> None:
-        self._cmd: Optional[cmd2.Cmd] = None
+        # Private reference to the CLI instance in which this CommandSet running.
+        # This will be set when the CommandSet is registered and it should be
+        # accessed by child classes using the self._cmd property.
+        self.__cmd_internal: Optional[cmd2.Cmd] = None
+
         self._settables: Dict[str, Settable] = {}
         self._settable_prefix = self.__class__.__name__
 
+    @property
+    def _cmd(self) -> 'cmd2.Cmd':
+        """
+        Property for child classes to access self.__cmd_internal.
+
+        Using this property ensures that self.__cmd_internal has been set
+        and it tells type checkers that it's no longer a None type.
+
+        Override this property if you need to change its return type to a
+        child class of Cmd.
+
+        :raises: CommandSetRegistrationError if CommandSet is not registered.
+        """
+        if self.__cmd_internal is None:
+            raise CommandSetRegistrationError('This CommandSet is not registered')
+        return self.__cmd_internal
+
     def on_register(self, cmd: 'cmd2.Cmd') -> None:
         """
         Called by cmd2.Cmd as the first step to registering a CommandSet. The commands defined in this class have
@@ -103,9 +124,10 @@ def on_register(self, cmd: 'cmd2.Cmd') -> None:
         requiring access to the Cmd object (e.g. configure commands and their parsers based on CLI state data).
 
         :param cmd: The cmd2 main application
+        :raises: CommandSetRegistrationError if CommandSet is already registered.
         """
-        if self._cmd is None:
-            self._cmd = cmd
+        if self.__cmd_internal is None:
+            self.__cmd_internal = cmd
         else:
             raise CommandSetRegistrationError('This CommandSet has already been registered')
 
@@ -129,7 +151,7 @@ def on_unregistered(self) -> None:
         Called by ``cmd2.Cmd`` after a CommandSet has been unregistered and all its commands removed from the CLI.
         Subclasses can override this to perform remaining cleanup steps.
         """
-        self._cmd = None
+        self.__cmd_internal = None
 
     @property
     def settable_prefix(self) -> str:
@@ -145,7 +167,7 @@ def add_settable(self, settable: Settable) -> None:
 
         :param settable: Settable object being added
         """
-        if self._cmd:
+        if self.__cmd_internal is not None:
             if not self._cmd.always_prefix_settables:
                 if settable.name in self._cmd.settables.keys() and settable.name not in self._settables.keys():
                     raise KeyError(f'Duplicate settable: {settable.name}')
diff --git a/tests_isolated/test_commandset/test_commandset.py b/tests_isolated/test_commandset/test_commandset.py
index da46c5d1..36384abd 100644
--- a/tests_isolated/test_commandset/test_commandset.py
+++ b/tests_isolated/test_commandset/test_commandset.py
@@ -150,8 +150,14 @@ def test_autoload_commands(command_sets_app):
 
 
 def test_custom_construct_commandsets():
-    # Verifies that a custom initialized CommandSet loads correctly when passed into the constructor
     command_set_b = CommandSetB('foo')
+
+    # Verify that _cmd cannot be accessed until CommandSet is registered.
+    with pytest.raises(CommandSetRegistrationError) as excinfo:
+        command_set_b._cmd.poutput("test")
+    assert "is not registered" in str(excinfo.value)
+
+    # Verifies that a custom initialized CommandSet loads correctly when passed into the constructor
     app = WithCommandSets(command_sets=[command_set_b])
 
     cmds_cats, cmds_doc, cmds_undoc, help_topics = app._build_command_info()