diff --git a/lib/solaar/dbus.py b/lib/solaar/dbus.py
index d470184a1f..ff4e58a695 100644
--- a/lib/solaar/dbus.py
+++ b/lib/solaar/dbus.py
@@ -14,9 +14,12 @@
 ## You should have received a copy of the GNU General Public License along
 ## with this program; if not, write to the Free Software Foundation, Inc.,
 ## 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+from __future__ import annotations
 
 import logging
 
+from typing import Callable
+
 logger = logging.getLogger(__name__)
 
 try:
@@ -49,14 +52,22 @@ def _suspend_or_resume(suspend):
 _LOGIND_INTERFACE = "org.freedesktop.login1.Manager"
 
 
-def watch_suspend_resume(on_resume_callback=None, on_suspend_callback=None):
+def watch_suspend_resume(
+    on_resume_callback: Callable[[], None] | None = None,
+    on_suspend_callback: Callable[[], None] | None = None,
+):
     """Register callback for suspend/resume events.
     They are called only if the system DBus is running, and the Login daemon is available."""
     global _resume_callback, _suspend_callback
     _suspend_callback = on_suspend_callback
     _resume_callback = on_resume_callback
     if bus is not None and on_resume_callback is not None or on_suspend_callback is not None:
-        bus.add_signal_receiver(_suspend_or_resume, "PrepareForSleep", dbus_interface=_LOGIND_INTERFACE, path=_LOGIND_PATH)
+        bus.add_signal_receiver(
+            _suspend_or_resume,
+            "PrepareForSleep",
+            dbus_interface=_LOGIND_INTERFACE,
+            path=_LOGIND_PATH,
+        )
     if logger.isEnabledFor(logging.INFO):
         logger.info("connected to system dbus, watching for suspend/resume events")
 
diff --git a/lib/solaar/ui/__init__.py b/lib/solaar/ui/__init__.py
index 890d7dccd7..1510db0023 100644
--- a/lib/solaar/ui/__init__.py
+++ b/lib/solaar/ui/__init__.py
@@ -17,6 +17,8 @@
 
 import logging
 
+from typing import Callable
+
 import gi
 import yaml
 
@@ -43,6 +45,9 @@
 assert Gtk.get_major_version() > 2, "Solaar requires Gtk 3 python bindings"
 
 
+APP_ID = "io.github.pwr_solaar.solaar"
+
+
 def _startup(app, startup_hook, use_tray, show_window):
     if logger.isEnabledFor(logging.DEBUG):
         logger.debug("startup registered=%s, remote=%s", app.get_is_registered(), app.get_is_remote())
@@ -88,12 +93,21 @@ def _shutdown(app, shutdown_hook):
     desktop_notifications.uninit()
 
 
-def run_loop(startup_hook, shutdown_hook, use_tray, show_window):
+def run_loop(
+    startup_hook: Callable[[], None],
+    shutdown_hook: Callable[[], None],
+    use_tray: bool,
+    show_window: bool,
+):
     assert use_tray or show_window, "need either tray or visible window"
-    APP_ID = "io.github.pwr_solaar.solaar"
+
     application = Gtk.Application.new(APP_ID, Gio.ApplicationFlags.HANDLES_COMMAND_LINE)
 
-    application.connect("startup", lambda app, startup_hook: _startup(app, startup_hook, use_tray, show_window), startup_hook)
+    application.connect(
+        "startup",
+        lambda app, startup_hook: _startup(app, startup_hook, use_tray, show_window),
+        startup_hook,
+    )
     application.connect("command-line", _command_line)
     application.connect("activate", _activate)
     application.connect("shutdown", _shutdown, shutdown_hook)