diff --git a/qutebrowser/mainwindow/statusbar/zoom.py b/qutebrowser/mainwindow/statusbar/zoom.py
index e059ca05b..fd0ed8129 100644
--- a/qutebrowser/mainwindow/statusbar/zoom.py
+++ b/qutebrowser/mainwindow/statusbar/zoom.py
@@ -1,25 +1,25 @@
 """Zoom percentage displayed in the statusbar."""
 
+from qutebrowser.browser import browsertab
 from qutebrowser.mainwindow.statusbar import textbase
-
-from qutebrowser.qt.core import pyqtSlot
+from qutebrowser.qt.core import pyqtSlot, QObject
 
 
 class Zoom(textbase.TextBase):
 
     """Shows percentage indicator."""
 
-    def __init__(self, parent=None):
+    def __init__(self, parent: QObject = None) -> None:
         super().__init__(parent)
         self.setText("100%")
 
     @pyqtSlot(float)
-    def on_zoom_changed(self, factor):
+    def on_zoom_changed(self, factor: float) -> None:
         """Update percentage when factor changed."""
         percentage = int(100 * factor)
         self.setText(f"{percentage}%")
 
-    def on_tab_changed(self, tab):
+    def on_tab_changed(self, tab: browsertab.AbstractTab) -> None:
         """Update percentage when tab changed."""
         percentage = int(100 * tab.zoom.factor())
 
diff --git a/tests/unit/mainwindow/statusbar/test_zoom.py b/tests/unit/mainwindow/statusbar/test_zoom.py
index d4ae0780f..48370b996 100644
--- a/tests/unit/mainwindow/statusbar/test_zoom.py
+++ b/tests/unit/mainwindow/statusbar/test_zoom.py
@@ -3,10 +3,12 @@
 import pytest
 
 from qutebrowser.mainwindow.statusbar.zoom import Zoom
+from typing import Any
+import pytestqt.qtbot
 
 
 @pytest.fixture
-def zoom(qtbot):
+def zoom(qtbot: pytestqt.qtbot.QtBot) -> Zoom:
     """Fixture providing a Percentage widget."""
     widget = Zoom()
     qtbot.add_widget(widget)
@@ -20,7 +22,7 @@ def zoom(qtbot):
     (0.5, '50%'),
     (0.25, '25%'),
 ])
-def test_percentage_texts(zoom, factor, expected):
+def test_percentage_texts(zoom: Zoom, factor: float, expected: str) -> None:
     """Test text displayed by the widget based on the zoom factor of a tab.
 
     Args:
@@ -31,7 +33,7 @@ def test_percentage_texts(zoom, factor, expected):
     assert zoom.text() == expected
 
 
-def test_tab_change(zoom, fake_web_tab):
+def test_tab_change(zoom: Zoom, fake_web_tab: Any) -> None:
     """Test zoom factor change when switching tabs."""
     zoom.on_zoom_changed(factor=2)
     assert zoom.text() == '200%'