diff --git a/lib/auth/auth.go b/lib/auth/auth.go
index 21cd351b1172..fb9077460d61 100644
--- a/lib/auth/auth.go
+++ b/lib/auth/auth.go
@@ -3829,13 +3829,7 @@ func (a *Server) deleteMFADeviceSafely(ctx context.Context, user, deviceName str
 		return nil, trace.Wrap(err)
 	}
 
-	kindToSF := map[string]constants.SecondFactorType{
-		fmt.Sprintf("%T", &types.MFADevice_Totp{}):     constants.SecondFactorOTP,
-		fmt.Sprintf("%T", &types.MFADevice_U2F{}):      constants.SecondFactorWebauthn,
-		fmt.Sprintf("%T", &types.MFADevice_Webauthn{}): constants.SecondFactorWebauthn,
-	}
-	sfToCount := make(map[constants.SecondFactorType]int)
-	var knownDevices int
+	knownDevices := make(map[constants.SecondFactorType]int)
 	var deviceToDelete *types.MFADevice
 	var numResidentKeys int
 
@@ -3850,18 +3844,26 @@ func (a *Server) deleteMFADeviceSafely(ctx context.Context, user, deviceName str
 			deviceToDelete = d
 		}
 
-		sf, ok := kindToSF[fmt.Sprintf("%T", d.Device)]
-		switch {
-		case !ok && d == deviceToDelete:
-			return nil, trace.NotImplemented("cannot delete device of type %T", d.Device)
-		case !ok:
+		var sfType constants.SecondFactorType
+		switch d.Device.(type) {
+		case *types.MFADevice_Totp:
+			sfType = constants.SecondFactorOTP
+		case *types.MFADevice_U2F, *types.MFADevice_Webauthn:
+			sfType = constants.SecondFactorWebauthn
+		case *types.MFADevice_Sso:
+			// TODO(Joerger): sso will not be supported in the current `second_factor` option.
+			// It will be supported in the new `second_factors` option instead, which will not
+			// use the old constants.SecondFactorType type. This will be handled in a separate PR.
+			sfType = "sso"
+			if d == deviceToDelete {
+				return nil, trace.BadParameter("cannot delete ephemeral SSO MFA device")
+			}
+		default:
 			log.Warnf("Ignoring unknown device with type %T in deletion.", d.Device)
 			continue
 		}
 
-		sfToCount[sf]++
-		knownDevices++
-
+		knownDevices[sfType]++
 		if isResidentKey(d) {
 			numResidentKeys++
 		}
@@ -3875,12 +3877,12 @@ func (a *Server) deleteMFADeviceSafely(ctx context.Context, user, deviceName str
 	switch sf := readOnlyAuthPref.GetSecondFactor(); sf {
 	case constants.SecondFactorOff, constants.SecondFactorOptional: // MFA is not required, allow deletion
 	case constants.SecondFactorOn:
-		if knownDevices <= minDevices {
+		if len(knownDevices) <= minDevices {
 			return nil, trace.BadParameter(
 				"cannot delete the last MFA device for this user; add a replacement device first to avoid getting locked out")
 		}
 	case constants.SecondFactorOTP, constants.SecondFactorWebauthn:
-		if sfToCount[sf] <= minDevices {
+		if knownDevices[sf] <= minDevices {
 			return nil, trace.BadParameter(
 				"cannot delete the last %s device for this user; add a replacement device first to avoid getting locked out", sf)
 		}
@@ -3909,7 +3911,7 @@ func (a *Server) deleteMFADeviceSafely(ctx context.Context, user, deviceName str
 
 		// Minimum number of WebAuthn devices includes the passkey that we attempt
 		// to delete, hence 2.
-		if sfToCount[constants.SecondFactorWebauthn] >= 2 {
+		if knownDevices[constants.SecondFactorWebauthn] >= 2 {
 			return true, nil
 		}
 
@@ -3917,7 +3919,7 @@ func (a *Server) deleteMFADeviceSafely(ctx context.Context, user, deviceName str
 		// enabled.
 		switch sf := readOnlyAuthPref.GetSecondFactor(); sf {
 		case constants.SecondFactorOTP, constants.SecondFactorOn, constants.SecondFactorOptional:
-			if sfToCount[constants.SecondFactorOTP] >= 1 {
+			if knownDevices[constants.SecondFactorOTP] >= 1 {
 				return true, nil
 			}
 		}
diff --git a/lib/auth/grpcserver_test.go b/lib/auth/grpcserver_test.go
index 36ec662c2588..27c754fc6f42 100644
--- a/lib/auth/grpcserver_test.go
+++ b/lib/auth/grpcserver_test.go
@@ -295,7 +295,7 @@ func TestMFADeviceManagement(t *testing.T) {
 	// 2nd-to-last resident credential.
 	// This is already tested above so we just use RegisterTestDevice here.
 	const pwdless2DevName = "pwdless2"
-	_, err = RegisterTestDevice(ctx, userClient, pwdless2DevName, proto.DeviceType_DEVICE_TYPE_WEBAUTHN, devs.WebDev, WithPasswordless())
+	pwdlessDev, err := RegisterTestDevice(ctx, userClient, pwdless2DevName, proto.DeviceType_DEVICE_TYPE_WEBAUTHN, devs.WebDev, WithPasswordless())
 	require.NoError(t, err, "RegisterTestDevice failed")
 
 	// Check that all new devices are registered.
@@ -433,6 +433,51 @@ func TestMFADeviceManagement(t *testing.T) {
 	resp, err = userClient.GetMFADevices(ctx, &proto.GetMFADevicesRequest{})
 	require.NoError(t, err)
 	require.Equal(t, "pwdless2", resp.Devices[0].GetName())
+
+	// Change the user to an SSO user with an MFA enabled auth connector.
+	samlConnector, err := types.NewSAMLConnector("saml", types.SAMLConnectorSpecV2{
+		AssertionConsumerService: "http://localhost:65535/acs", // not called
+		Issuer:                   "test",
+		SSO:                      "https://localhost:65535/sso", // not called
+		AttributesToRoles: []types.AttributeMapping{
+			// not used. can be any name, value but role must exist
+			{Name: "groups", Value: "admin", Roles: user.GetRoles()},
+		},
+		MFASettings: &types.SAMLConnectorMFASettings{
+			Enabled: true,
+		},
+	})
+	require.NoError(t, err)
+	_, err = authServer.UpsertSAMLConnector(ctx, samlConnector)
+	require.NoError(t, err)
+	user.SetCreatedBy(types.CreatedBy{
+		Time: authServer.clock.Now(),
+		Connector: &types.ConnectorRef{
+			ID:   "saml",
+			Type: "saml",
+		},
+	})
+	_, err = authServer.UpsertUser(ctx, user)
+	require.NoError(t, err)
+
+	// Ephemeral sso device should show up in the list now. It can't be deleted.
+	resp, err = userClient.GetMFADevices(ctx, &proto.GetMFADevicesRequest{})
+	require.NoError(t, err)
+	require.Len(t, resp.Devices, 2)
+
+	testDeleteMFADevice(ctx, t, userClient, mfaDeleteTestOpts{
+		deviceName: "saml",
+		authHandler: func(t *testing.T, challenge *proto.MFAAuthenticateChallenge) *proto.MFAAuthenticateResponse {
+			require.NotNil(t, challenge.WebauthnChallenge, "nil Webauthn challenge")
+			mfaResp, err := pwdlessDev.SolveAuthn(challenge)
+			require.NoError(t, err, "SolveAuthn")
+			return mfaResp
+		},
+		checkErr: func(t require.TestingT, err error, _ ...interface{}) {
+			require.ErrorAs(t, err, new(*trace.BadParameterError))
+			require.ErrorContains(t, err, "cannot delete ephemeral SSO MFA device")
+		}},
+	)
 }
 
 func TestDeletingLastPasswordlessDevice(t *testing.T) {