diff --git a/pyecobee/__init__.py b/pyecobee/__init__.py
index a99f155..0837bc2 100644
--- a/pyecobee/__init__.py
+++ b/pyecobee/__init__.py
@@ -93,9 +93,9 @@ def _generate_pkce_pair() -> tuple[str, str]:
 class MfaChallenge:
     """Opaque resumption state for an in-progress MFA-gated login.
 
-    Returned (via :class:`EcobeeAuthMfaRequiredError`) when ecobee Auth0
-    interrupts the login flow with an MFA challenge. Pass this back into
-    :meth:`Ecobee.submit_mfa_code` along with the user-entered code to
+    Returned via :attr:`EcobeeAuthMfaRequiredError.challenge` when ecobee
+    Auth0 interrupts the login flow with an MFA challenge. Pass this back
+    into :meth:`Ecobee.submit_mfa_code` along with the user-entered code to
     complete the login and obtain tokens.
     """
 
diff --git a/pyecobee/errors.py b/pyecobee/errors.py
index 0abcae2..1bc4899 100644
--- a/pyecobee/errors.py
+++ b/pyecobee/errors.py
@@ -26,11 +26,18 @@ class EcobeeAuthUnknownError(EcobeeError):
 class EcobeeAuthMfaRequiredError(EcobeeError):
     """Raised when ecobee Auth0 redirects to an MFA challenge during login.
 
-    Carries an :class:`~pyecobee.MfaChallenge` payload (in ``args[0]``) that
-    must be passed back into :meth:`Ecobee.submit_mfa_code` along with the
-    user-entered OTP code to resume the login flow.
+    Carries an :class:`~pyecobee.MfaChallenge` payload that must be passed
+    back into :meth:`Ecobee.submit_mfa_code` along with the user-entered OTP
+    code to resume the login flow.
+
+    Prefer :attr:`challenge` over indexing ``args[0]``.
     """
 
+    @property
+    def challenge(self):
+        """Return the :class:`~pyecobee.MfaChallenge` carried by this error."""
+        return self.args[0]
+
 
 # Sensor errors
 class InvalidSensorError(EcobeeError):
diff --git a/setup.py b/setup.py
index de7f9a4..4e9617e 100755
--- a/setup.py
+++ b/setup.py
@@ -34,7 +34,7 @@
 
 setup(
     name="python-ecobee-api",
-    version="0.4.1",
+    version="0.4.2",
     description="Python API for talking to Ecobee thermostats",
     url="https://github.com/nkgilley/python-ecobee-api",
     author="Nolan Gilley",
diff --git a/tests/test_auth.py b/tests/test_auth.py
index 4403ecd..7e1fb10 100644
--- a/tests/test_auth.py
+++ b/tests/test_auth.py
@@ -209,7 +209,8 @@ def test_request_tokens_web_mfa_required_raises_with_challenge(
     ecobee = _make_ecobee()
     with pytest.raises(EcobeeAuthMfaRequiredError) as exc_info:
         ecobee.request_tokens_web()
-    challenge = exc_info.value.args[0]
+    challenge = exc_info.value.challenge
+    assert challenge is exc_info.value.args[0]
     assert isinstance(challenge, MfaChallenge)
     assert challenge.mfa_type == "otp"
     assert challenge.state == "MFA_STATE_9"
@@ -237,7 +238,8 @@ def test_request_tokens_web_sms_mfa_required_raises_with_challenge(
     ecobee = _make_ecobee()
     with pytest.raises(EcobeeAuthMfaRequiredError) as exc_info:
         ecobee.request_tokens_web()
-    challenge = exc_info.value.args[0]
+    challenge = exc_info.value.challenge
+    assert challenge is exc_info.value.args[0]
     assert isinstance(challenge, MfaChallenge)
     assert challenge.mfa_type == "sms"
     assert challenge.state == "SMS_STATE_7"