diff --git a/mypy.ini b/mypy.ini
index 797ed0bca..91c314675 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -10,6 +10,7 @@ warn_unused_ignores = True
 disallow_subclassing_any = True
 # disallow_untyped_calls = True
 # disallow_untyped_defs = True
+# https://github.com/python/mypy/issues/5954
 # disallow_incomplete_defs = True
 # check_untyped_defs = True
 # disallow_untyped_decorators = True
diff --git a/qutebrowser/browser/browsertab.py b/qutebrowser/browser/browsertab.py
index 0cd54be7e..02d9b70dd 100644
--- a/qutebrowser/browser/browsertab.py
+++ b/qutebrowser/browser/browsertab.py
@@ -685,7 +685,7 @@ class AbstractAudio(QObject):
         self._widget = None
         self._tab = tab
 
-    def set_muted(self, muted: bool, override: bool = False):
+    def set_muted(self, muted: bool, override: bool = False) -> None:
         """Set this tab as muted or not.
 
         Arguments:
@@ -699,7 +699,7 @@ class AbstractAudio(QObject):
         """Whether this tab is muted."""
         raise NotImplementedError
 
-    def toggle_muted(self, *, override: bool = False):
+    def toggle_muted(self, *, override: bool = False) -> None:
         self.set_muted(not self.is_muted(), override=override)
 
     def is_recently_audible(self):
diff --git a/qutebrowser/browser/commands.py b/qutebrowser/browser/commands.py
index 2af938fb5..5c97aaf53 100644
--- a/qutebrowser/browser/commands.py
+++ b/qutebrowser/browser/commands.py
@@ -513,7 +513,8 @@ class CommandDispatcher:
     @cmdutils.register(instance='command-dispatcher', scope='window')
     @cmdutils.argument('win_id', completion=miscmodels.window)
     @cmdutils.argument('count', count=True)
-    def tab_give(self, win_id: int = None, keep=False, count=None):
+    def tab_give(self, win_id: int = None, keep: bool = False,
+                 count: int = None) -> None:
         """Give the current tab to a new or existing window if win_id given.
 
         If no win_id is given, the tab will get detached into a new window.
@@ -601,7 +602,8 @@ class CommandDispatcher:
     @cmdutils.argument('where', choices=['prev', 'next', 'up', 'increment',
                                          'decrement'])
     @cmdutils.argument('count', count=True)
-    def navigate(self, where: str, tab=False, bg=False, window=False, count=1):
+    def navigate(self, where: str, tab: bool = False, bg: bool = False,
+                 window: bool = False, count: int = 1) -> None:
         """Open typical prev/next links or navigate using the URL path.
 
         This tries to automatically click on typical _Previous Page_ or
@@ -665,7 +667,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
     @cmdutils.argument('count', count=True)
-    def scroll_px(self, dx: int, dy: int, count=1):
+    def scroll_px(self, dx: int, dy: int, count: int = 1) -> None:
         """Scroll the current tab by 'count * dx/dy' pixels.
 
         Args:
@@ -681,7 +683,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
     @cmdutils.argument('count', count=True)
-    def scroll(self, direction: str, count=1):
+    def scroll(self, direction: str, count: int = 1) -> None:
         """Scroll the current tab in the given direction.
 
         Note you can use `:run-with-count` to have a keybinding with a bigger
@@ -719,7 +721,8 @@ class CommandDispatcher:
     @cmdutils.register(instance='command-dispatcher', scope='window')
     @cmdutils.argument('count', count=True)
     @cmdutils.argument('horizontal', flag='x')
-    def scroll_to_perc(self, perc: float = None, horizontal=False, count=None):
+    def scroll_to_perc(self, perc: float = None, horizontal: bool = False,
+                       count: int = None) -> None:
         """Scroll to a specific percentage of the page.
 
         The percentage can be given either as argument or as count.
@@ -764,7 +767,7 @@ class CommandDispatcher:
                        choices=('next', 'increment'))
     def scroll_page(self, x: float, y: float, *,
                     top_navigate: str = None, bottom_navigate: str = None,
-                    count=1):
+                    count: int = 1) -> None:
         """Scroll the frame page-wise.
 
         Args:
@@ -1120,7 +1123,7 @@ class CommandDispatcher:
     @cmdutils.argument('index', choices=['last'])
     @cmdutils.argument('count', count=True)
     def tab_focus(self, index: typing.Union[str, int] = None,
-                  count=None, no_last=False):
+                  count: int = None, no_last: bool = False) -> None:
         """Select the tab given as argument/[count].
 
         If neither count nor index are given, it behaves like tab-next.
@@ -1161,7 +1164,8 @@ class CommandDispatcher:
     @cmdutils.register(instance='command-dispatcher', scope='window')
     @cmdutils.argument('index', choices=['+', '-'])
     @cmdutils.argument('count', count=True)
-    def tab_move(self, index: typing.Union[str, int] = None, count=None):
+    def tab_move(self, index: typing.Union[str, int] = None,
+                 count: int = None) -> None:
         """Move the current tab according to the argument and [count].
 
         If neither is given, move it to the first position.
@@ -1718,10 +1722,10 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
     @cmdutils.argument('filter_', choices=['id'])
-    def click_element(self, filter_: str, value, *,
+    def click_element(self, filter_: str, value: str, *,
                       target: usertypes.ClickTarget =
                       usertypes.ClickTarget.normal,
-                      force_event=False):
+                      force_event: bool = False) -> None:
         """Click the element matching the given filter.
 
         The given filter needs to result in exactly one element, otherwise, an
@@ -2070,8 +2074,8 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window',
                        maxsplit=0, no_cmd_split=True)
-    def jseval(self, js_code, file=False, quiet=False, *,
-               world: typing.Union[usertypes.JsWorld, int] = None):
+    def jseval(self, js_code: str, file: bool = False, quiet: bool = False, *,
+               world: typing.Union[usertypes.JsWorld, int] = None) -> None:
         """Evaluate a JavaScript string.
 
         Args:
diff --git a/qutebrowser/browser/downloads.py b/qutebrowser/browser/downloads.py
index 9c2a88a87..1709c7425 100644
--- a/qutebrowser/browser/downloads.py
+++ b/qutebrowser/browser/downloads.py
@@ -1062,7 +1062,7 @@ class DownloadModel(QAbstractListModel):
 
     @cmdutils.register(instance='download-model', scope='window', maxsplit=0)
     @cmdutils.argument('count', count=True)
-    def download_open(self, cmdline: str = None, count=0):
+    def download_open(self, cmdline: str = None, count: int = 0) -> None:
         """Open the last/[count]th download.
 
         If no specific command is given, this will use the system's default
diff --git a/qutebrowser/browser/webengine/webenginetab.py b/qutebrowser/browser/webengine/webenginetab.py
index 0f1d368e9..9945886fa 100644
--- a/qutebrowser/browser/webengine/webenginetab.py
+++ b/qutebrowser/browser/webengine/webenginetab.py
@@ -670,7 +670,7 @@ class WebEngineAudio(browsertab.AbstractAudio):
         self._tab.url_changed.connect(self._on_url_changed)
         config.instance.changed.connect(self._on_config_changed)
 
-    def set_muted(self, muted: bool, override: bool = False):
+    def set_muted(self, muted: bool, override: bool = False) -> None:
         self._overridden = override
         page = self._widget.page()
         page.setAudioMuted(muted)
diff --git a/qutebrowser/browser/webengine/webview.py b/qutebrowser/browser/webengine/webview.py
index b10cc5f9a..e70226f30 100644
--- a/qutebrowser/browser/webengine/webview.py
+++ b/qutebrowser/browser/webengine/webview.py
@@ -240,7 +240,7 @@ class WebEnginePage(QWebEnginePage):
     def acceptNavigationRequest(self,
                                 url: QUrl,
                                 typ: QWebEnginePage.NavigationType,
-                                is_main_frame: bool):
+                                is_main_frame: bool) -> bool:
         """Override acceptNavigationRequest to forward it to the tab API."""
         type_map = {
             QWebEnginePage.NavigationTypeLinkClicked:
diff --git a/qutebrowser/browser/webkit/webkittab.py b/qutebrowser/browser/webkit/webkittab.py
index 2edea1777..c791326ce 100644
--- a/qutebrowser/browser/webkit/webkittab.py
+++ b/qutebrowser/browser/webkit/webkittab.py
@@ -641,7 +641,7 @@ class WebKitAudio(browsertab.AbstractAudio):
 
     """Dummy handling of audio status for QtWebKit."""
 
-    def set_muted(self, muted: bool, override: bool = False):
+    def set_muted(self, muted: bool, override: bool = False) -> None:
         raise browsertab.WebTabError('Muting is not supported on QtWebKit!')
 
     def is_muted(self):
diff --git a/qutebrowser/browser/webkit/webpage.py b/qutebrowser/browser/webkit/webpage.py
index ce985b466..0195ec17f 100644
--- a/qutebrowser/browser/webkit/webpage.py
+++ b/qutebrowser/browser/webkit/webpage.py
@@ -469,7 +469,7 @@ class BrowserPage(QWebPage):
     def acceptNavigationRequest(self,
                                 frame: QWebFrame,
                                 request: QNetworkRequest,
-                                typ: QWebPage.NavigationType):
+                                typ: QWebPage.NavigationType) -> bool:
         """Override acceptNavigationRequest to handle clicked links.
 
         Setting linkDelegationPolicy to DelegateAllLinks and using a slot bound
diff --git a/qutebrowser/config/configcache.py b/qutebrowser/config/configcache.py
index cdba6456a..a421ba85c 100644
--- a/qutebrowser/config/configcache.py
+++ b/qutebrowser/config/configcache.py
@@ -45,7 +45,7 @@ class ConfigCache:
         if attr in self._cache:
             self._cache[attr] = config.instance.get(attr)
 
-    def __getitem__(self, attr: str):
+    def __getitem__(self, attr: str) -> typing.Any:
         if attr not in self._cache:
             assert not config.instance.get_opt(attr).supports_pattern
             self._cache[attr] = config.instance.get(attr)
diff --git a/qutebrowser/mainwindow/prompt.py b/qutebrowser/mainwindow/prompt.py
index 5eb76c86e..f6a8b1224 100644
--- a/qutebrowser/mainwindow/prompt.py
+++ b/qutebrowser/mainwindow/prompt.py
@@ -391,7 +391,8 @@ class PromptContainer(QWidget):
 
     @cmdutils.register(instance='prompt-container', scope='window',
                        modes=[usertypes.KeyMode.prompt], maxsplit=0)
-    def prompt_open_download(self, cmdline: str = None, pdfjs=False):
+    def prompt_open_download(self, cmdline: str = None,
+                             pdfjs: bool = False) -> None:
         """Immediately open a download.
 
         If no specific command is given, this will use the system's default
diff --git a/qutebrowser/mainwindow/tabwidget.py b/qutebrowser/mainwindow/tabwidget.py
index f9c2ac0e6..a3ba0f1da 100644
--- a/qutebrowser/mainwindow/tabwidget.py
+++ b/qutebrowser/mainwindow/tabwidget.py
@@ -342,7 +342,7 @@ class TabWidget(QTabWidget):
         qtutils.ensure_valid(url)
         return url
 
-    def update_tab_favicon(self, tab: QWidget):
+    def update_tab_favicon(self, tab: QWidget) -> None:
         """Update favicon of the given tab."""
         idx = self.indexOf(tab)
 
@@ -400,7 +400,7 @@ class TabBar(QTabBar):
         return self.parent().currentWidget()
 
     @pyqtSlot(str)
-    def _on_config_changed(self, option: str):
+    def _on_config_changed(self, option: str) -> None:
         if option == 'fonts.tabs':
             self._set_font()
         elif option == 'tabs.favicons.scale':
@@ -543,7 +543,7 @@ class TabBar(QTabBar):
             return
         super().mousePressEvent(e)
 
-    def minimumTabSizeHint(self, index, ellipsis: bool = True) -> QSize:
+    def minimumTabSizeHint(self, index: int, ellipsis: bool = True) -> QSize:
         """Set the minimum tab size to indicator/icon/... text.
 
         Args:
@@ -623,7 +623,7 @@ class TabBar(QTabBar):
             return False
         return widget.data.pinned
 
-    def tabSizeHint(self, index: int):
+    def tabSizeHint(self, index: int) -> QSize:
         """Override tabSizeHint to customize qb's tab size.
 
         https://wiki.python.org/moin/PyQt/Customising%20tab%20bars
diff --git a/qutebrowser/misc/sessions.py b/qutebrowser/misc/sessions.py
index 9d3736cdb..b94566830 100644
--- a/qutebrowser/misc/sessions.py
+++ b/qutebrowser/misc/sessions.py
@@ -511,9 +511,12 @@ class SessionManager(QObject):
     @cmdutils.argument('win_id', win_id=True)
     @cmdutils.argument('with_private', flag='p')
     def session_save(self, name: typing.Union[str, Sentinel] = default,
-                     current=False, quiet=False, force=False,
-                     only_active_window=False, with_private=False,
-                     win_id=None):
+                     current: bool = False,
+                     quiet: bool = False,
+                     force: bool = False,
+                     only_active_window: bool = False,
+                     with_private: bool = False,
+                     win_id: int = None) -> None:
         """Save a session.
 
         Args:
diff --git a/qutebrowser/misc/utilcmds.py b/qutebrowser/misc/utilcmds.py
index b8d8be447..b893c8d6e 100644
--- a/qutebrowser/misc/utilcmds.py
+++ b/qutebrowser/misc/utilcmds.py
@@ -44,7 +44,7 @@ from qutebrowser.qt import sip
 
 @cmdutils.register(maxsplit=1, no_cmd_split=True, no_replace_variables=True)
 @cmdutils.argument('win_id', win_id=True)
-def later(ms: int, command, win_id):
+def later(ms: int, command: str, win_id: int) -> None:
     """Execute a command after some time.
 
     Args:
@@ -75,7 +75,7 @@ def later(ms: int, command, win_id):
 @cmdutils.register(maxsplit=1, no_cmd_split=True, no_replace_variables=True)
 @cmdutils.argument('win_id', win_id=True)
 @cmdutils.argument('count', count=True)
-def repeat(times: int, command, win_id, count=None):
+def repeat(times: int, command: str, win_id: int, count: int = None) -> None:
     """Repeat a given command.
 
     Args:
@@ -96,7 +96,8 @@ def repeat(times: int, command, win_id, count=None):
 @cmdutils.register(maxsplit=1, no_cmd_split=True, no_replace_variables=True)
 @cmdutils.argument('win_id', win_id=True)
 @cmdutils.argument('count', count=True)
-def run_with_count(count_arg: int, command, win_id, count=1):
+def run_with_count(count_arg: int, command: str, win_id: int,
+                   count: int = 1) -> None:
     """Run a command with the given count.
 
     If run_with_count itself is run with a count, it multiplies count_arg.
@@ -303,7 +304,7 @@ def repeat_command(win_id, count=None):
 
 
 @cmdutils.register(debug=True, name='debug-log-capacity')
-def log_capacity(capacity: int):
+def log_capacity(capacity: int) -> None:
     """Change the number of log lines to be stored in RAM.
 
     Args:
@@ -320,7 +321,7 @@ def log_capacity(capacity: int):
 @cmdutils.argument('level', choices=sorted(
     (level.lower() for level in log.LOG_LEVELS),
     key=lambda e: log.LOG_LEVELS[e.upper()]))
-def debug_log_level(level: str):
+def debug_log_level(level: str) -> None:
     """Change the log level for console logging.
 
     Args:
@@ -332,7 +333,7 @@ def debug_log_level(level: str):
 
 
 @cmdutils.register(debug=True)
-def debug_log_filter(filters: str):
+def debug_log_filter(filters: str) -> None:
     """Change the log filter for console logging.
 
     Args: