diff --git a/pg_backup_api/pg_backup_api/logic/utility_controller.py b/pg_backup_api/pg_backup_api/logic/utility_controller.py
index b84c788..dff02a1 100644
--- a/pg_backup_api/pg_backup_api/logic/utility_controller.py
+++ b/pg_backup_api/pg_backup_api/logic/utility_controller.py
@@ -40,6 +40,8 @@
 
 if TYPE_CHECKING:  # pragma: no cover
     from flask import Request, Response
+    from barman.config import Config as BarmanConfig
+    from pg_backup_api.server_operation import Operation
 
 
 @app.route("/diagnose", methods=["GET"])
@@ -53,11 +55,15 @@ def diagnose() -> 'Response':
     """
     # Reload the barman config so that any changes are picked up
     load_barman_config()
+
+    if TYPE_CHECKING:  # pragma: no cover
+        assert isinstance(barman.__config__, BarmanConfig)
+
     # Get every server (both inactive and temporarily disabled)
     servers = barman.__config__.server_names()
 
     server_dict = {}
-    for server in servers:
+    for server in servers:  # pyright: ignore
         conf = barman.__config__.get_server(server)
         if conf is None:
             # Unknown server
@@ -214,6 +220,9 @@ def servers_operations_post(server_name: str,
         )
         subprocess.Popen(cmd.split())
 
+    if TYPE_CHECKING:  # pragma: no cover
+        assert isinstance(operation, Operation)
+
     return {"operation_id": operation.id}
 
 
diff --git a/pg_backup_api/pg_backup_api/server_operation.py b/pg_backup_api/pg_backup_api/server_operation.py
index b79c143..52cf028 100644
--- a/pg_backup_api/pg_backup_api/server_operation.py
+++ b/pg_backup_api/pg_backup_api/server_operation.py
@@ -30,7 +30,7 @@
 import os
 import subprocess
 import sys
-from typing import (Any, Callable, Dict, List, Optional, Set, Tuple,
+from typing import (Any, Callable, Dict, List, Optional, Set, Tuple, Union,
                     TYPE_CHECKING)
 
 from datetime import datetime
@@ -494,7 +494,8 @@ def get_status(self) -> str:
         return self.server.get_operation_status(self.id)
 
     @staticmethod
-    def _run_subprocess(cmd: List[str]) -> Tuple[Optional[str], int]:
+    def _run_subprocess(cmd: List[str]) -> \
+            Tuple[Union[str, bytearray, memoryview], Union[int, Any]]:
         """
         Run *cmd* as a subprocess.
 
@@ -512,7 +513,8 @@ def _run_subprocess(cmd: List[str]) -> Tuple[Optional[str], int]:
         return stdout, process.returncode
 
     @abstractmethod
-    def _run_logic(self) -> Tuple[Optional[str], int]:
+    def _run_logic(self) -> \
+            Tuple[Union[str, bytearray, memoryview], Union[int, Any]]:
         """
         Logic to be ran when executing the operation.
 
@@ -526,7 +528,7 @@ def _run_logic(self) -> Tuple[Optional[str], int]:
         """
         pass
 
-    def run(self) -> Tuple[Optional[str], int]:
+    def run(self) -> Tuple[Union[str, bytearray, memoryview], Union[int, Any]]:
         """
         Run the operation.
 
@@ -621,7 +623,8 @@ def _get_args(self) -> List[str]:
             remote_ssh_command,
         ]
 
-    def _run_logic(self) -> Tuple[Optional[str], int]:
+    def _run_logic(self) -> \
+            Tuple[Union[str, bytearray, memoryview], Union[int, Any]]:
         """
         Logic to be ran when executing the recovery operation.
 
diff --git a/pg_backup_api/pg_backup_api/utils.py b/pg_backup_api/pg_backup_api/utils.py
index ce1ec7b..736c3e4 100644
--- a/pg_backup_api/pg_backup_api/utils.py
+++ b/pg_backup_api/pg_backup_api/utils.py
@@ -34,7 +34,8 @@
 
 if TYPE_CHECKING:  # pragma: no cover
     import flask.app
-    from barman.config import ServerConfig
+    from barman.config import Config as BarmanConfig, ServerConfig
+    import barman.server
 
 
 CONFIG_FILENAME = "/etc/barman.conf"
@@ -98,7 +99,10 @@ def get_server_by_name(server_name: str) -> Optional['ServerConfig']:
     :return: configuration of Barman server *server_name* if that server
         exists, ``None`` otherwise.
     """
-    for server in barman.__config__.server_names():
+    if TYPE_CHECKING:  # pragma: no cover
+        assert isinstance(barman.__config__, BarmanConfig)
+
+    for server in barman.__config__.server_names():  # pyright: ignore
         conf = barman.__config__.get_server(server)
         if server == server_name:
             return conf
@@ -120,11 +124,13 @@ def parse_backup_id(server: barman.server.Server,
     :return: information about the backup, if *backup_id* can be satisfied,
         ``None`` otherwise.
     """
+    parsed_backup_id = backup_id
+
     if backup_id in ("latest", "last"):
-        backup_id = server.get_last_backup_id()
+        parsed_backup_id = server.get_last_backup_id()
     elif backup_id in ("oldest", "first"):
-        backup_id = server.get_first_backup_id()
+        parsed_backup_id = server.get_first_backup_id()
     elif backup_id in ("last-failed"):
-        backup_id = server.get_last_backup_id([BackupInfo.FAILED])
+        parsed_backup_id = server.get_last_backup_id([BackupInfo.FAILED])
 
-    return server.get_backup(backup_id)
+    return server.get_backup(parsed_backup_id)