diff --git a/ops/model.py b/ops/model.py
index 141bd4f..2ab4ff8 100644
--- a/ops/model.py
+++ b/ops/model.py
@@ -276,6 +276,9 @@ class Model:
         """
         if not (id or label):
             raise TypeError('Must provide an id or label, or both')
+        if id is not None:
+            # Canonicalize to "secret:<id>" form for consistency in backend calls.
+            id = Secret._canonicalize_id(id)
         try:
             content = self._backend.secret_get(id=id, label=label)
             return Secret(self._backend, id=id, label=label, content=content)

diff --git a/test/test_model.py b/test/test_model.py
index 976fb77..35df7ea 100755
--- a/test/test_model.py
+++ b/test/test_model.py
@@ -2841,7 +2841,18 @@ class TestSecrets(unittest.TestCase):
         self.assertEqual(secret.get_content(), {'foo': 'g'})
 
         self.assertEqual(fake_script_calls(self, clear=True),
-                         [['secret-get', '123', '--format=json']])
+                         [['secret-get', 'secret:123', '--format=json']])
+
+    def test_get_secret_label(self):
+        fake_script(self, 'secret-get', """echo '{"foo": "g"}'""")
+
+        secret = self.model.get_secret(label='lbl')
+        self.assertIsNone(secret.id)
+        self.assertEqual(secret.label, 'lbl')
+        self.assertEqual(secret.get_content(), {'foo': 'g'})
+
+        self.assertEqual(fake_script_calls(self, clear=True),
+                         [['secret-get', '--label', 'lbl', '--format=json']])
 
     def test_get_secret_id_and_label(self):
         fake_script(self, 'secret-get', """echo '{"foo": "h"}'""")
@@ -2852,7 +2863,7 @@ class TestSecrets(unittest.TestCase):
         self.assertEqual(secret.get_content(), {'foo': 'h'})
 
         self.assertEqual(fake_script_calls(self, clear=True),
-                         [['secret-get', '123', '--label', 'l', '--format=json']])
+                         [['secret-get', 'secret:123', '--label', 'l', '--format=json']])
 
     def test_get_secret_no_args(self):
         with self.assertRaises(TypeError):

secret id is not always canonicalized before calling secret_get
Secret canonicalizes the ID it receives upon initialization.
However, before the Secret object is initialized, the ID is used to call secret_get. This results in the ID being sometimes canonicalized, sometimes not, depending on the caller.

For example:
```
self.model.get_secret(id="foo").get_content()
# resulting call: secret-get --id foo

self.model.get_secret(id="foo").peek_content()
# resulting call: secret-get --id secret:foo --peek
```

This is not a problem per se, but it might mean headache in the future. 
test/test_model.py::TestSecrets::test_get_secret_id test/test_model.py::TestSecrets::test_get_secret_id_and_label
test/test_model.py::TestModel::test_active_message_default test/test_model.py::TestModel::test_app_immutable test/test_model.py::TestModel::test_app_relation_data_modify_local_as_leader test/test_model.py::TestModel::test_app_relation_data_modify_local_as_minion test/test_model.py::TestModel::test_base_status_instance_raises test/test_model.py::TestModel::test_config test/test_model.py::TestModel::test_config_immutable test/test_model.py::TestModel::test_get_app_relation_data test/test_model.py::TestModel::test_get_relation test/test_model.py::TestModel::test_invalid_type_relation_data test/test_model.py::TestModel::test_is_leader test/test_model.py::TestModel::test_local_set_valid_app_status test/test_model.py::TestModel::test_local_set_valid_unit_status test/test_model.py::TestModel::test_model_attributes test/test_model.py::TestModel::test_model_name_from_backend test/test_model.py::TestModel::test_our_unit_is_our test/test_model.py::TestModel::test_peer_relation_app test/test_model.py::TestModel::test_pod_immutable test/test_model.py::TestModel::test_pod_spec test/test_model.py::TestModel::test_relation_data_access_peer_leader test/test_model.py::TestModel::test_relation_data_access_peer_minion test/test_model.py::TestModel::test_relation_data_del_key test/test_model.py::TestModel::test_relation_data_del_missing_key test/test_model.py::TestModel::test_relation_data_modify_our test/test_model.py::TestModel::test_relation_data_modify_remote test/test_model.py::TestModel::test_relation_data_type_check test/test_model.py::TestModel::test_relation_local_app_data_readability_follower test/test_model.py::TestModel::test_relation_local_app_data_readability_leader test/test_model.py::TestModel::test_relation_no_units test/test_model.py::TestModel::test_relation_set_fail test/test_model.py::TestModel::test_relations_immutable test/test_model.py::TestModel::test_relations_keys test/test_model.py::TestModel::test_remote_app_relation_data test/test_model.py::TestModel::test_remote_app_status test/test_model.py::TestModel::test_remote_unit_status test/test_model.py::TestModel::test_remote_units_is_our test/test_model.py::TestModel::test_resources test/test_model.py::TestModel::test_resources_immutable test/test_model.py::TestModel::test_run_error test/test_model.py::TestModel::test_set_app_status_invalid test/test_model.py::TestModel::test_set_app_status_non_leader_raises test/test_model.py::TestModel::test_set_unit_status_invalid test/test_model.py::TestModel::test_status_eq test/test_model.py::TestModel::test_status_repr test/test_model.py::TestModel::test_storage test/test_model.py::TestModel::test_storages_immutable test/test_model.py::TestModel::test_unit_immutable test/test_model.py::TestModel::test_unit_relation_data test/test_model.py::TestModel::test_workload_version test/test_model.py::TestModel::test_workload_version_invalid test/test_model.py::test_recursive_list[case0] test/test_model.py::test_recursive_list[case1] test/test_model.py::test_recursive_list[case2] test/test_model.py::test_recursive_push_and_pull[case0] test/test_model.py::test_recursive_push_and_pull[case1] test/test_model.py::test_recursive_push_and_pull[case2] test/test_model.py::test_recursive_push_and_pull[case3] test/test_model.py::test_recursive_push_and_pull[case4] test/test_model.py::test_recursive_push_and_pull[case5] test/test_model.py::test_recursive_push_and_pull[case6] test/test_model.py::test_recursive_push_and_pull[case7] test/test_model.py::test_recursive_push_and_pull[case8] test/test_model.py::TestApplication::test_mocked_get_services test/test_model.py::TestApplication::test_planned_units test/test_model.py::TestApplication::test_planned_units_garbage_values test/test_model.py::TestApplication::test_planned_units_override test/test_model.py::TestApplication::test_planned_units_user_set test/test_model.py::TestContainers::test_unit_containers test/test_model.py::TestContainers::test_unit_get_container test/test_model.py::TestContainerPebble::test_add_layer test/test_model.py::TestContainerPebble::test_autostart test/test_model.py::TestContainerPebble::test_can_connect test/test_model.py::TestContainerPebble::test_can_connect_api_error test/test_model.py::TestContainerPebble::test_can_connect_connection_error test/test_model.py::TestContainerPebble::test_can_connect_file_not_found_error test/test_model.py::TestContainerPebble::test_can_connect_simple test/test_model.py::TestContainerPebble::test_exec test/test_model.py::TestContainerPebble::test_get_check test/test_model.py::TestContainerPebble::test_get_checks test/test_model.py::TestContainerPebble::test_get_plan test/test_model.py::TestContainerPebble::test_get_service test/test_model.py::TestContainerPebble::test_get_services test/test_model.py::TestContainerPebble::test_list_files test/test_model.py::TestContainerPebble::test_make_dir test/test_model.py::TestContainerPebble::test_pull test/test_model.py::TestContainerPebble::test_push test/test_model.py::TestContainerPebble::test_remove_path test/test_model.py::TestContainerPebble::test_replan test/test_model.py::TestContainerPebble::test_restart test/test_model.py::TestContainerPebble::test_restart_fallback test/test_model.py::TestContainerPebble::test_restart_fallback_non_400_error test/test_model.py::TestContainerPebble::test_restart_no_arguments test/test_model.py::TestContainerPebble::test_send_signal test/test_model.py::TestContainerPebble::test_socket_path test/test_model.py::TestContainerPebble::test_start test/test_model.py::TestContainerPebble::test_start_no_arguments test/test_model.py::TestContainerPebble::test_stop test/test_model.py::TestContainerPebble::test_stop_no_arguments test/test_model.py::TestContainerPebble::test_type_errors test/test_model.py::TestModelBindings::test_binding_by_relation test/test_model.py::TestModelBindings::test_binding_by_relation_name test/test_model.py::TestModelBindings::test_binding_no_iface_name test/test_model.py::TestModelBindings::test_dead_relations test/test_model.py::TestModelBindings::test_empty_bind_addresses test/test_model.py::TestModelBindings::test_empty_interface_info test/test_model.py::TestModelBindings::test_invalid_keys test/test_model.py::TestModelBindings::test_missing_bind_addresses test/test_model.py::TestModelBindings::test_missing_egress_subnets test/test_model.py::TestModelBindings::test_missing_ingress_addresses test/test_model.py::TestModelBindings::test_no_bind_addresses test/test_model.py::TestModelBindings::test_unresolved_ingress_addresses test/test_model.py::TestModelBackend::test_action_fail test/test_model.py::TestModelBackend::test_action_get test/test_model.py::TestModelBackend::test_action_get_error test/test_model.py::TestModelBackend::test_action_log test/test_model.py::TestModelBackend::test_action_log_error test/test_model.py::TestModelBackend::test_action_set test/test_model.py::TestModelBackend::test_action_set_dotted_dict test/test_model.py::TestModelBackend::test_action_set_duplicated_keys test/test_model.py::TestModelBackend::test_action_set_error test/test_model.py::TestModelBackend::test_action_set_key_validation test/test_model.py::TestModelBackend::test_action_set_more_nested test/test_model.py::TestModelBackend::test_action_set_nested test/test_model.py::TestModelBackend::test_application_version_set test/test_model.py::TestModelBackend::test_application_version_set_invalid test/test_model.py::TestModelBackend::test_invalid_metric_label_values test/test_model.py::TestModelBackend::test_invalid_metric_labels test/test_model.py::TestModelBackend::test_invalid_metric_names test/test_model.py::TestModelBackend::test_invalid_metric_values test/test_model.py::TestModelBackend::test_is_leader_refresh test/test_model.py::TestModelBackend::test_juju_log test/test_model.py::TestModelBackend::test_local_get_status test/test_model.py::TestModelBackend::test_local_set_invalid_status test/test_model.py::TestModelBackend::test_network_get test/test_model.py::TestModelBackend::test_network_get_errors test/test_model.py::TestModelBackend::test_relation_get_juju_version_quirks test/test_model.py::TestModelBackend::test_relation_get_set_is_app_arg test/test_model.py::TestModelBackend::test_relation_remote_app_name_env test/test_model.py::TestModelBackend::test_relation_remote_app_name_script_errors test/test_model.py::TestModelBackend::test_relation_remote_app_name_script_success test/test_model.py::TestModelBackend::test_relation_set_juju_version_quirks test/test_model.py::TestModelBackend::test_relation_tool_errors test/test_model.py::TestModelBackend::test_status_get test/test_model.py::TestModelBackend::test_status_is_app_forced_kwargs test/test_model.py::TestModelBackend::test_status_set_is_app_not_bool_raises test/test_model.py::TestModelBackend::test_storage_tool_errors test/test_model.py::TestModelBackend::test_valid_metrics test/test_model.py::TestLazyMapping::test_invalidate test/test_model.py::TestSecrets::test_add_secret_errors test/test_model.py::TestSecrets::test_app_add_secret_args test/test_model.py::TestSecrets::test_app_add_secret_simple test/test_model.py::TestSecrets::test_get_secret_label test/test_model.py::TestSecrets::test_get_secret_no_args test/test_model.py::TestSecrets::test_get_secret_not_found test/test_model.py::TestSecrets::test_get_secret_other_error test/test_model.py::TestSecrets::test_unit_add_secret_args test/test_model.py::TestSecrets::test_unit_add_secret_errors test/test_model.py::TestSecrets::test_unit_add_secret_simple test/test_model.py::TestSecretInfo::test_from_dict test/test_model.py::TestSecretInfo::test_init test/test_model.py::TestSecretClass::test_get_content_cached test/test_model.py::TestSecretClass::test_get_content_refresh test/test_model.py::TestSecretClass::test_get_content_uncached test/test_model.py::TestSecretClass::test_get_info test/test_model.py::TestSecretClass::test_grant test/test_model.py::TestSecretClass::test_id_and_label test/test_model.py::TestSecretClass::test_peek_content test/test_model.py::TestSecretClass::test_remove_all_revisions test/test_model.py::TestSecretClass::test_remove_revision test/test_model.py::TestSecretClass::test_revoke test/test_model.py::TestSecretClass::test_set_content test/test_model.py::TestSecretClass::test_set_info