diff --git a/doc/contributing.asciidoc b/doc/contributing.asciidoc
index 5f0e9bf9c..399633257 100644
--- a/doc/contributing.asciidoc
+++ b/doc/contributing.asciidoc
@@ -480,8 +480,9 @@ For `typing.Union` types, the given `choices` are only checked if other types
 The following arguments are supported for `@cmdutils.argument`:
 
 - `flag`: Customize the short flag (`-x`) the argument will get.
-- `win_id=True`: Mark the argument as special window ID argument.
-- `count=True`: Mark the argument as special count argument.
+- `value`: Tell qutebrowser to fill the argument with special values:
+   - `value=cmdutils.Value.count`: The `count` given by the user to the command.
+   - `value=cmdutils.Value.win_id`: The window ID of the current window.
 - `completion`: A completion function (see `qutebrowser.completions.models.*`)
   to use when completing arguments for the given command.
 - `choices`: The allowed string choices for the argument.
diff --git a/qutebrowser/api/cmdutils.py b/qutebrowser/api/cmdutils.py
index 10acf9b4d..796c74eba 100644
--- a/qutebrowser/api/cmdutils.py
+++ b/qutebrowser/api/cmdutils.py
@@ -21,9 +21,12 @@
 
 import inspect
 import typing
+import enum
 
 from qutebrowser.utils import qtutils
 from qutebrowser.commands import command, cmdexc
+# pylint: disable=unused-import
+from qutebrowser.utils.usertypes import CommandValue as Value
 
 
 class CommandError(cmdexc.Error):
diff --git a/qutebrowser/browser/commands.py b/qutebrowser/browser/commands.py
index 63c2da3b3..f4703850a 100644
--- a/qutebrowser/browser/commands.py
+++ b/qutebrowser/browser/commands.py
@@ -230,7 +230,7 @@ class CommandDispatcher:
             tabbar.setSelectionBehaviorOnRemove(old_selection_behavior)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def tab_close(self, prev=False, next_=False, opposite=False,
                   force=False, count=None):
         """Close the current/[count]th tab.
@@ -253,7 +253,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window',
                        name='tab-pin')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def tab_pin(self, count=None):
         """Pin/Unpin the current/[count]th tab.
 
@@ -274,7 +274,7 @@ class CommandDispatcher:
     @cmdutils.register(instance='command-dispatcher', name='open',
                        maxsplit=0, scope='window')
     @cmdutils.argument('url', completion=urlmodel.url)
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def openurl(self, url=None, related=False,
                 bg=False, tab=False, window=False, count=None, secure=False,
                 private=False):
@@ -372,7 +372,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', name='reload',
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def reloadpage(self, force=False, count=None):
         """Reload the current/[count]th tab.
 
@@ -385,7 +385,7 @@ class CommandDispatcher:
             tab.reload(force=force)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def stop(self, count=None):
         """Stop loading in the current/[count]th tab.
 
@@ -423,7 +423,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', name='print',
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     @cmdutils.argument('pdf', flag='f', metavar='file')
     def printpage(self, preview=False, count=None, *, pdf=None):
         """Print the current/[count]th tab.
@@ -514,7 +514,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
     @cmdutils.argument('win_id', completion=miscmodels.window)
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     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.
@@ -575,7 +575,7 @@ class CommandDispatcher:
             raise cmdutils.CommandError(e)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def back(self, tab=False, bg=False, window=False, count=1):
         """Go back in the history of the current tab.
 
@@ -588,7 +588,7 @@ class CommandDispatcher:
         self._back_forward(tab, bg, window, count, forward=False)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def forward(self, tab=False, bg=False, window=False, count=1):
         """Go forward in the history of the current tab.
 
@@ -603,7 +603,7 @@ class CommandDispatcher:
     @cmdutils.register(instance='command-dispatcher', scope='window')
     @cmdutils.argument('where', choices=['prev', 'next', 'up', 'increment',
                                          'decrement'])
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     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.
@@ -668,7 +668,7 @@ class CommandDispatcher:
             raise cmdutils.CommandError(e)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def scroll_px(self, dx: int, dy: int, count: int = 1) -> None:
         """Scroll the current tab by 'count * dx/dy' pixels.
 
@@ -684,7 +684,7 @@ class CommandDispatcher:
         self._current_widget().scroller.delta(dx, dy)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def scroll(self, direction: str, count: int = 1) -> None:
         """Scroll the current tab in the given direction.
 
@@ -721,7 +721,7 @@ class CommandDispatcher:
             func(count=count)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     @cmdutils.argument('horizontal', flag='x')
     def scroll_to_perc(self, perc: float = None, horizontal: bool = False,
                        count: int = None) -> None:
@@ -762,7 +762,7 @@ class CommandDispatcher:
         self._current_widget().scroller.to_anchor(name)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     @cmdutils.argument('top_navigate', metavar='ACTION',
                        choices=('prev', 'decrement'))
     @cmdutils.argument('bottom_navigate', metavar='ACTION',
@@ -891,7 +891,7 @@ class CommandDispatcher:
                               maybe=True)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def zoom_in(self, count=1, quiet=False):
         """Increase the zoom level for the current tab.
 
@@ -908,7 +908,7 @@ class CommandDispatcher:
             message.info("Zoom level: {}%".format(int(perc)), replace=True)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def zoom_out(self, count=1, quiet=False):
         """Decrease the zoom level for the current tab.
 
@@ -925,7 +925,7 @@ class CommandDispatcher:
             message.info("Zoom level: {}%".format(int(perc)), replace=True)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def zoom(self, zoom=None, count=None, quiet=False):
         """Set the zoom level for the current tab.
 
@@ -1005,7 +1005,7 @@ class CommandDispatcher:
             raise cmdutils.CommandError("Nothing to undo!")
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def tab_prev(self, count=1):
         """Switch to the previous tab, or switch [count] tabs back.
 
@@ -1025,7 +1025,7 @@ class CommandDispatcher:
             log.webview.debug("First tab")
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def tab_next(self, count=1):
         """Switch to the next tab, or switch [count] tabs forward.
 
@@ -1093,7 +1093,7 @@ class CommandDispatcher:
     @cmdutils.register(instance='command-dispatcher', scope='window',
                        maxsplit=0)
     @cmdutils.argument('index', completion=miscmodels.buffer)
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def buffer(self, index=None, count=None):
         """Select tab by index or url/title best match.
 
@@ -1123,7 +1123,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
     @cmdutils.argument('index', choices=['last'])
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def tab_focus(self, index: typing.Union[str, int] = None,
                   count: int = None, no_last: bool = False) -> None:
         """Select the tab given as argument/[count].
@@ -1165,7 +1165,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
     @cmdutils.argument('index', choices=['+', '-'])
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def tab_move(self, index: typing.Union[str, int] = None,
                  count: int = None) -> None:
         """Move the current tab according to the argument and [count].
@@ -1212,7 +1212,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window',
                        maxsplit=0, no_replace_variables=True)
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def spawn(self, cmdline, userscript=False, verbose=False,
               output=False, detach=False, count=None):
         """Spawn a command in a shell.
@@ -1830,7 +1830,7 @@ class CommandDispatcher:
         tab.search.search(text, **options)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def search_next(self, count=1):
         """Continue the search to the ([count]th) next term.
 
@@ -1864,7 +1864,7 @@ class CommandDispatcher:
         tab.search.next_result(result_cb=cb)
 
     @cmdutils.register(instance='command-dispatcher', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def search_prev(self, count=1):
         """Continue the search to the ([count]th) previous term.
 
@@ -1899,7 +1899,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_next_line(self, count=1):
         """Move the cursor or selection to the next line.
 
@@ -1910,7 +1910,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_prev_line(self, count=1):
         """Move the cursor or selection to the prev line.
 
@@ -1921,7 +1921,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_next_char(self, count=1):
         """Move the cursor or selection to the next char.
 
@@ -1932,7 +1932,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_prev_char(self, count=1):
         """Move the cursor or selection to the previous char.
 
@@ -1943,7 +1943,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_end_of_word(self, count=1):
         """Move the cursor or selection to the end of the word.
 
@@ -1954,7 +1954,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_next_word(self, count=1):
         """Move the cursor or selection to the next word.
 
@@ -1965,7 +1965,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_prev_word(self, count=1):
         """Move the cursor or selection to the previous word.
 
@@ -1988,7 +1988,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_start_of_next_block(self, count=1):
         """Move the cursor or selection to the start of next block.
 
@@ -1999,7 +1999,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_start_of_prev_block(self, count=1):
         """Move the cursor or selection to the start of previous block.
 
@@ -2010,7 +2010,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_end_of_next_block(self, count=1):
         """Move the cursor or selection to the end of next block.
 
@@ -2021,7 +2021,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', modes=[KeyMode.caret],
                        scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def move_to_end_of_prev_block(self, count=1):
         """Move the cursor or selection to the end of previous block.
 
@@ -2056,7 +2056,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window',
                        debug=True)
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def debug_webaction(self, action, count=1):
         """Execute a webaction.
 
@@ -2256,7 +2256,7 @@ class CommandDispatcher:
 
     @cmdutils.register(instance='command-dispatcher', scope='window',
                        name='tab-mute')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def tab_mute(self, count=None):
         """Mute/Unmute the current/[count]th tab.
 
diff --git a/qutebrowser/browser/downloads.py b/qutebrowser/browser/downloads.py
index 6d9fa6c4e..b18e426d7 100644
--- a/qutebrowser/browser/downloads.py
+++ b/qutebrowser/browser/downloads.py
@@ -1013,7 +1013,7 @@ class DownloadModel(QAbstractListModel):
         raise cmdutils.CommandError("There's no download {}!".format(count))
 
     @cmdutils.register(instance='download-model', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def download_cancel(self, all_=False, count=0):
         """Cancel the last/[count]th download.
 
@@ -1039,7 +1039,7 @@ class DownloadModel(QAbstractListModel):
             download.cancel()
 
     @cmdutils.register(instance='download-model', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def download_delete(self, count=0):
         """Delete the last/[count]th download from disk.
 
@@ -1060,7 +1060,7 @@ class DownloadModel(QAbstractListModel):
         log.downloads.debug("deleted download {}".format(download))
 
     @cmdutils.register(instance='download-model', scope='window', maxsplit=0)
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def download_open(self, cmdline: str = None, count: int = 0) -> None:
         """Open the last/[count]th download.
 
@@ -1086,7 +1086,7 @@ class DownloadModel(QAbstractListModel):
         download.open_file(cmdline)
 
     @cmdutils.register(instance='download-model', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def download_retry(self, count=0):
         """Retry the first failed/[count]th download.
 
@@ -1121,7 +1121,7 @@ class DownloadModel(QAbstractListModel):
                 download.remove()
 
     @cmdutils.register(instance='download-model', scope='window')
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def download_remove(self, all_=False, count=0):
         """Remove the last/[count]th download from the list.
 
diff --git a/qutebrowser/commands/command.py b/qutebrowser/commands/command.py
index 811bc78eb..a318897d5 100644
--- a/qutebrowser/commands/command.py
+++ b/qutebrowser/commands/command.py
@@ -37,18 +37,13 @@ class ArgInfo:
 
     """Information about an argument."""
 
-    win_id = attr.ib(False)
-    count = attr.ib(False)
+    value = attr.ib(None)
     hide = attr.ib(False)
     metavar = attr.ib(None)
     flag = attr.ib(None)
     completion = attr.ib(None)
     choices = attr.ib(None)
 
-    def __attrs_post_init__(self):
-        if self.win_id and self.count:
-            raise TypeError("Argument marked as both count/win_id!")
-
 
 class Command:
 
@@ -116,7 +111,6 @@ class Command:
         self.parser.add_argument('-h', '--help', action=argparser.HelpAction,
                                  default=argparser.SUPPRESS, nargs=0,
                                  help=argparser.SUPPRESS)
-        self._check_func()
         self.opt_args = collections.OrderedDict()
         self.namespace = None
         self._count = None
@@ -130,6 +124,7 @@ class Command:
         self._qute_args = getattr(self.handler, 'qute_args', {})
         self.handler.qute_args = None
 
+        self._check_func()
         self._inspect_func()
 
     def _check_prerequisites(self, win_id):
@@ -154,9 +149,14 @@ class Command:
     def _check_func(self):
         """Make sure the function parameters don't violate any rules."""
         signature = inspect.signature(self.handler)
-        if 'self' in signature.parameters and self._instance is None:
-            raise TypeError("{} is a class method, but instance was not "
-                            "given!".format(self.name[0]))
+        if 'self' in signature.parameters:
+            if self._instance is None:
+                raise TypeError("{} is a class method, but instance was not "
+                                "given!".format(self.name[0]))
+            arg_info = self.get_arg_info(signature.parameters['self'])
+            if arg_info.value is not None:
+                raise TypeError("{}: Can't fill 'self' with value!"
+                                .format(self.name))
         elif 'self' not in signature.parameters and self._instance is not None:
             raise TypeError("{} is not a class method, but instance was "
                             "given!".format(self.name[0]))
@@ -186,13 +186,18 @@ class Command:
             True if the parameter is special, False otherwise.
         """
         arg_info = self.get_arg_info(param)
-        if arg_info.count:
+        if arg_info.value is None:
+            return False
+        elif arg_info.value == usertypes.CommandValue.count:
             if param.default is inspect.Parameter.empty:
                 raise TypeError("{}: handler has count parameter "
                                 "without default!".format(self.name))
             return True
-        elif arg_info.win_id:
+        elif arg_info.value == usertypes.CommandValue.win_id:
             return True
+        else:
+            raise TypeError("{}: Invalid value={!r} for argument '{}'!"
+                            .format(self.name, arg_info.value, param.name))
         return False
 
     def _inspect_func(self):
@@ -325,9 +330,8 @@ class Command:
             return param.annotation
         elif param.default not in [None, inspect.Parameter.empty]:
             return type(param.default)
-        elif arginfo.count or arginfo.win_id or param.kind in [
-                inspect.Parameter.VAR_POSITIONAL,
-                inspect.Parameter.VAR_KEYWORD]:
+        elif arginfo.value or param.kind in [inspect.Parameter.VAR_POSITIONAL,
+                                             inspect.Parameter.VAR_KEYWORD]:
             return None
         else:
             return str
@@ -447,15 +451,13 @@ class Command:
                 # Special case for 'self'.
                 self._get_self_arg(win_id, param, args)
                 continue
-            elif arg_info.count:
-                # Special case for count parameter.
+            elif arg_info.value == usertypes.CommandValue.count:
                 self._get_count_arg(param, args, kwargs)
                 continue
-            # elif arg_info.win_id:
-            elif arg_info.win_id:
-                # Special case for win_id parameter.
+            elif arg_info.value == usertypes.CommandValue.win_id:
                 self._get_win_id_arg(win_id, param, args, kwargs)
                 continue
+
             value = self._get_param_value(param)
             if param.kind == inspect.Parameter.POSITIONAL_OR_KEYWORD:
                 args.append(value)
diff --git a/qutebrowser/config/configcommands.py b/qutebrowser/config/configcommands.py
index 74a381507..574bc06af 100644
--- a/qutebrowser/config/configcommands.py
+++ b/qutebrowser/config/configcommands.py
@@ -79,7 +79,7 @@ class ConfigCommands:
     @cmdutils.register(instance='config-commands')
     @cmdutils.argument('option', completion=configmodel.option)
     @cmdutils.argument('value', completion=configmodel.value)
-    @cmdutils.argument('win_id', win_id=True)
+    @cmdutils.argument('win_id', value=cmdutils.Value.win_id)
     @cmdutils.argument('pattern', flag='u')
     def set(self, win_id, option=None, value=None, temp=False, print_=False,
             *, pattern=None):
@@ -127,7 +127,7 @@ class ConfigCommands:
     @cmdutils.register(instance='config-commands', maxsplit=1,
                        no_cmd_split=True, no_replace_variables=True)
     @cmdutils.argument('command', completion=configmodel.bind)
-    @cmdutils.argument('win_id', win_id=True)
+    @cmdutils.argument('win_id', value=cmdutils.Value.win_id)
     def bind(self, win_id, key=None, command=None, *, mode='normal',
              default=False):
         """Bind a key to a command.
diff --git a/qutebrowser/keyinput/macros.py b/qutebrowser/keyinput/macros.py
index bd17f5664..5bf1ab18b 100644
--- a/qutebrowser/keyinput/macros.py
+++ b/qutebrowser/keyinput/macros.py
@@ -45,7 +45,7 @@ class MacroRecorder:
         self._last_register = None
 
     @cmdutils.register(instance='macro-recorder', name='record-macro')
-    @cmdutils.argument('win_id', win_id=True)
+    @cmdutils.argument('win_id', value=cmdutils.Value.win_id)
     def record_macro_command(self, win_id, register=None):
         """Start or stop recording a macro.
 
@@ -70,8 +70,8 @@ class MacroRecorder:
         self._recording_macro = register
 
     @cmdutils.register(instance='macro-recorder', name='run-macro')
-    @cmdutils.argument('win_id', win_id=True)
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('win_id', value=cmdutils.Value.win_id)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def run_macro_command(self, win_id, count=1, register=None):
         """Run a recorded macro.
 
diff --git a/qutebrowser/mainwindow/statusbar/command.py b/qutebrowser/mainwindow/statusbar/command.py
index de42cda4e..1661d2362 100644
--- a/qutebrowser/mainwindow/statusbar/command.py
+++ b/qutebrowser/mainwindow/statusbar/command.py
@@ -115,7 +115,7 @@ class Command(misc.MinimalLineEditMixin, misc.CommandLineEdit):
 
     @cmdutils.register(instance='status-command', name='set-cmd-text',
                        scope='window', maxsplit=0)
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def set_cmd_text_command(self, text, count=None, space=False, append=False,
                              run_on_count=False):
         """Preset the statusbar to some text.
diff --git a/qutebrowser/misc/sessions.py b/qutebrowser/misc/sessions.py
index 357d5be64..2a557ef50 100644
--- a/qutebrowser/misc/sessions.py
+++ b/qutebrowser/misc/sessions.py
@@ -508,7 +508,7 @@ class SessionManager(QObject):
 
     @cmdutils.register(instance='session-manager')
     @cmdutils.argument('name', completion=miscmodels.session)
-    @cmdutils.argument('win_id', win_id=True)
+    @cmdutils.argument('win_id', value=cmdutils.Value.win_id)
     @cmdutils.argument('with_private', flag='p')
     def session_save(self, name: typing.Union[str, Sentinel] = default,
                      current: bool = False,
diff --git a/qutebrowser/misc/utilcmds.py b/qutebrowser/misc/utilcmds.py
index 761498e5f..287704551 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)
+@cmdutils.argument('win_id', value=cmdutils.Value.win_id)
 def later(ms: int, command: str, win_id: int) -> None:
     """Execute a command after some time.
 
@@ -74,8 +74,8 @@ def later(ms: int, command: str, win_id: int) -> 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)
+@cmdutils.argument('win_id', value=cmdutils.Value.win_id)
+@cmdutils.argument('count', value=cmdutils.Value.count)
 def repeat(times: int, command: str, win_id: int, count: int = None) -> None:
     """Repeat a given command.
 
@@ -95,8 +95,8 @@ def repeat(times: int, command: str, win_id: int, count: int = None) -> 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)
+@cmdutils.argument('win_id', value=cmdutils.Value.win_id)
+@cmdutils.argument('count', value=cmdutils.Value.count)
 def run_with_count(count_arg: int, command: str, win_id: int,
                    count: int = 1) -> None:
     """Run a command with the given count.
@@ -122,7 +122,7 @@ def message_error(text):
 
 
 @cmdutils.register()
-@cmdutils.argument('count', count=True)
+@cmdutils.argument('count', value=cmdutils.Value.count)
 def message_info(text, count=1):
     """Show an info message in the statusbar.
 
@@ -288,8 +288,8 @@ def debug_set_fake_clipboard(s=None):
 
 
 @cmdutils.register()
-@cmdutils.argument('win_id', win_id=True)
-@cmdutils.argument('count', count=True)
+@cmdutils.argument('win_id', value=cmdutils.Value.win_id)
+@cmdutils.argument('count', value=cmdutils.Value.count)
 def repeat_command(win_id, count=None):
     """Repeat the last executed command.
 
@@ -358,7 +358,7 @@ def debug_log_filter(filters: str) -> None:
 
 
 @cmdutils.register()
-@cmdutils.argument('current_win_id', win_id=True)
+@cmdutils.argument('current_win_id', value=cmdutils.Value.win_id)
 def window_only(current_win_id):
     """Close all windows except for the current one."""
     for win_id, window in objreg.window_registry.items():
@@ -377,7 +377,7 @@ def nop():
 
 
 @cmdutils.register()
-@cmdutils.argument('win_id', win_id=True)
+@cmdutils.argument('win_id', value=cmdutils.Value.win_id)
 def version(win_id, paste=False):
     """Show version information.
 
diff --git a/qutebrowser/utils/usertypes.py b/qutebrowser/utils/usertypes.py
index 5bb8d3aa9..d8f46ded8 100644
--- a/qutebrowser/utils/usertypes.py
+++ b/qutebrowser/utils/usertypes.py
@@ -256,6 +256,14 @@ MessageLevel = enum.Enum('MessageLevel', ['error', 'warning', 'info'])
 IgnoreCase = enum.Enum('IgnoreCase', ['smart', 'never', 'always'])
 
 
+class CommandValue(enum.Enum):
+
+    """Special values which are injected when running a command handler."""
+
+    count = 1
+    win_id = 2
+
+
 class Question(QObject):
 
     """A question asked to the user, e.g. via the status bar.
diff --git a/tests/unit/api/test_cmdutils.py b/tests/unit/api/test_cmdutils.py
index f2318ab46..5e1389c80 100644
--- a/tests/unit/api/test_cmdutils.py
+++ b/tests/unit/api/test_cmdutils.py
@@ -190,23 +190,39 @@ class TestRegister:
 
     def test_win_id(self):
         @cmdutils.register()
-        @cmdutils.argument('win_id', win_id=True)
+        @cmdutils.argument('win_id', value=cmdutils.Value.win_id)
         def fun(win_id):
             """Blah."""
         assert objects.commands['fun']._get_call_args(42) == ([42], {})
 
     def test_count(self):
         @cmdutils.register()
-        @cmdutils.argument('count', count=True)
+        @cmdutils.argument('count', value=cmdutils.Value.count)
         def fun(count=0):
             """Blah."""
         assert objects.commands['fun']._get_call_args(42) == ([0], {})
 
+    def test_fill_self(self):
+        with pytest.raises(TypeError, match="fun: Can't fill 'self' with "
+                           "value!"):
+            @cmdutils.register(instance='foobar')
+            @cmdutils.argument('self', value=cmdutils.Value.count)
+            def fun(self):
+                """Blah."""
+
+    def test_fill_invalid(self):
+        with pytest.raises(TypeError, match="fun: Invalid value='foo' for "
+                           "argument 'arg'!"):
+            @cmdutils.register()
+            @cmdutils.argument('arg', value='foo')
+            def fun(arg):
+                """Blah."""
+
     def test_count_without_default(self):
         with pytest.raises(TypeError, match="fun: handler has count parameter "
                            "without default!"):
             @cmdutils.register()
-            @cmdutils.argument('count', count=True)
+            @cmdutils.argument('count', value=cmdutils.Value.count)
             def fun(count):
                 """Blah."""
 
@@ -344,6 +360,17 @@ class TestArgument:
         }
         assert fun.qute_args == expected
 
+    def test_arginfo_boolean(self):
+        @cmdutils.argument('special1', value=cmdutils.Value.count)
+        @cmdutils.argument('special2', value=cmdutils.Value.win_id)
+        @cmdutils.argument('normal')
+        def fun(special1, special2, normal):
+            """Blah."""
+
+        assert fun.qute_args['special1'].value
+        assert fun.qute_args['special2'].value
+        assert not fun.qute_args['normal'].value
+
     def test_wrong_order(self):
         """When @cmdutils.argument is used above (after) @register, fail."""
         with pytest.raises(ValueError, match=r"@cmdutils.argument got called "
@@ -353,13 +380,6 @@ class TestArgument:
             def fun(bar):
                 """Blah."""
 
-    def test_count_and_win_id_same_arg(self):
-        with pytest.raises(TypeError,
-                           match="Argument marked as both count/win_id!"):
-            @cmdutils.argument('arg', count=True, win_id=True)
-            def fun(arg=0):
-                """Blah."""
-
     def test_no_docstring(self, caplog):
         with caplog.at_level(logging.WARNING):
             @cmdutils.register()
diff --git a/tests/unit/completion/test_completer.py b/tests/unit/completion/test_completer.py
index 16ebb95dc..224268c90 100644
--- a/tests/unit/completion/test_completer.py
+++ b/tests/unit/completion/test_completer.py
@@ -112,12 +112,12 @@ def cmdutils_patch(monkeypatch, stubs, miscmodels_patch):
         """docstring."""
 
     @cmdutils.argument('url', completion=miscmodels_patch.url)
-    @cmdutils.argument('count', count=True)
+    @cmdutils.argument('count', value=cmdutils.Value.count)
     def openurl(url=None, related=False, bg=False, tab=False, window=False,
                 count=None):
         """docstring."""
 
-    @cmdutils.argument('win_id', win_id=True)
+    @cmdutils.argument('win_id', value=cmdutils.Value.win_id)
     @cmdutils.argument('command', completion=miscmodels_patch.command)
     def bind(key, win_id, command=None, *, mode='normal'):
         """docstring."""