diff --git a/electrum/base_wizard.py b/electrum/base_wizard.py
index 8cd7d4a11..f1ff514e5 100644
--- a/electrum/base_wizard.py
+++ b/electrum/base_wizard.py
@@ -535,6 +535,7 @@ class BaseWizard(Logger):
         if self.wallet_type == 'standard' and isinstance(self.keystores[0], Hardware_KeyStore):
             # offer encrypting with a pw derived from the hw device
             k = self.keystores[0]  # type: Hardware_KeyStore
+            assert isinstance(self.plugin, HW_PluginBase)
             try:
                 k.handler = self.plugin.create_handler(self)
                 password = k.get_password_for_storage_encryption()
diff --git a/electrum/gui/qt/installwizard.py b/electrum/gui/qt/installwizard.py
index ed470d571..88056d8ae 100644
--- a/electrum/gui/qt/installwizard.py
+++ b/electrum/gui/qt/installwizard.py
@@ -358,10 +358,6 @@ class InstallWizard(QDialog, MessageBoxMixin, BaseWizard):
 
         return db
 
-    def finished(self):
-        """Called in hardware client wrapper, in order to close popups."""
-        return
-
     def on_error(self, exc_info):
         if not isinstance(exc_info[1], UserCancelled):
             self.logger.error("on_error", exc_info=exc_info)
diff --git a/electrum/keystore.py b/electrum/keystore.py
index 7620edb2a..c0ec81c44 100644
--- a/electrum/keystore.py
+++ b/electrum/keystore.py
@@ -48,7 +48,7 @@ from .logging import Logger
 
 if TYPE_CHECKING:
     from .gui.qt.util import TaskThread
-    from .plugins.hw_wallet import HW_PluginBase, HardwareClientBase
+    from .plugins.hw_wallet import HW_PluginBase, HardwareClientBase, HardwareHandlerBase
 
 
 class KeyStore(Logger, ABC):
@@ -723,7 +723,7 @@ class Hardware_KeyStore(Xpub, KeyStore):
         # device reconnects
         self.xpub = d.get('xpub')
         self.label = d.get('label')
-        self.handler = None
+        self.handler = None  # type: Optional[HardwareHandlerBase]
         run_hook('init_keystore', self)
 
     def set_label(self, label):
diff --git a/electrum/plugin.py b/electrum/plugin.py
index 0bcc5d20e..c84cd9aea 100644
--- a/electrum/plugin.py
+++ b/electrum/plugin.py
@@ -39,7 +39,7 @@ from .simple_config import SimpleConfig
 from .logging import get_logger, Logger
 
 if TYPE_CHECKING:
-    from .plugins.hw_wallet import HW_PluginBase, HardwareClientBase
+    from .plugins.hw_wallet import HW_PluginBase, HardwareClientBase, HardwareHandlerBase
     from .keystore import Hardware_KeyStore
 
 
@@ -386,7 +386,8 @@ class DeviceMgr(ThreadJob):
     def register_enumerate_func(self, func):
         self.enumerate_func.add(func)
 
-    def create_client(self, device: 'Device', handler, plugin: 'HW_PluginBase') -> Optional['HardwareClientBase']:
+    def create_client(self, device: 'Device', handler: Optional['HardwareHandlerBase'],
+                      plugin: 'HW_PluginBase') -> Optional['HardwareClientBase']:
         # Get from cache first
         client = self.client_lookup(device.id_)
         if client:
@@ -447,7 +448,8 @@ class DeviceMgr(ThreadJob):
         self.scan_devices()
         return self.client_lookup(id_)
 
-    def client_for_keystore(self, plugin: 'HW_PluginBase', handler, keystore: 'Hardware_KeyStore',
+    def client_for_keystore(self, plugin: 'HW_PluginBase', handler: Optional['HardwareHandlerBase'],
+                            keystore: 'Hardware_KeyStore',
                             force_pair: bool) -> Optional['HardwareClientBase']:
         self.logger.info("getting client for keystore")
         if handler is None:
@@ -468,7 +470,7 @@ class DeviceMgr(ThreadJob):
         self.logger.info("end client for keystore")
         return client
 
-    def client_by_xpub(self, plugin: 'HW_PluginBase', xpub, handler,
+    def client_by_xpub(self, plugin: 'HW_PluginBase', xpub, handler: 'HardwareHandlerBase',
                        devices: Iterable['Device']) -> Optional['HardwareClientBase']:
         _id = self.xpub_id(xpub)
         client = self.client_lookup(_id)
@@ -482,7 +484,7 @@ class DeviceMgr(ThreadJob):
             if device.id_ == _id:
                 return self.create_client(device, handler, plugin)
 
-    def force_pair_xpub(self, plugin: 'HW_PluginBase', handler,
+    def force_pair_xpub(self, plugin: 'HW_PluginBase', handler: 'HardwareHandlerBase',
                         info: 'DeviceInfo', xpub, derivation) -> Optional['HardwareClientBase']:
         # The wallet has not been previously paired, so let the user
         # choose an unpaired device and compare its first address.
@@ -510,7 +512,8 @@ class DeviceMgr(ThreadJob):
               'its seed (and passphrase, if any).  Otherwise all bitcoins you '
               'receive will be unspendable.').format(plugin.device))
 
-    def unpaired_device_infos(self, handler, plugin: 'HW_PluginBase', devices: List['Device'] = None,
+    def unpaired_device_infos(self, handler: Optional['HardwareHandlerBase'], plugin: 'HW_PluginBase',
+                              devices: List['Device'] = None,
                               include_failing_clients=False) -> List['DeviceInfo']:
         '''Returns a list of DeviceInfo objects: one for each connected,
         unpaired device accepted by the plugin.'''
@@ -539,7 +542,7 @@ class DeviceMgr(ThreadJob):
 
         return infos
 
-    def select_device(self, plugin: 'HW_PluginBase', handler,
+    def select_device(self, plugin: 'HW_PluginBase', handler: 'HardwareHandlerBase',
                       keystore: 'Hardware_KeyStore', devices: List['Device'] = None) -> 'DeviceInfo':
         '''Ask the user to select a device to use if there is more than one,
         and return the DeviceInfo for the device.'''
@@ -581,8 +584,9 @@ class DeviceMgr(ThreadJob):
         info = infos[c]
         # save new label
         keystore.set_label(info.label)
-        if handler.win.wallet is not None:
-            handler.win.wallet.save_keystore()
+        wallet = handler.get_wallet()
+        if wallet is not None:
+            wallet.save_keystore()
         return info
 
     def _scan_devices_with_hid(self) -> List['Device']:
diff --git a/electrum/plugins/coldcard/cmdline.py b/electrum/plugins/coldcard/cmdline.py
index 6e6e69a21..7df86f1f2 100644
--- a/electrum/plugins/coldcard/cmdline.py
+++ b/electrum/plugins/coldcard/cmdline.py
@@ -2,13 +2,15 @@ from electrum.plugin import hook
 from electrum.util import print_msg, raw_input, print_stderr
 from electrum.logging import get_logger
 
+from ..hw_wallet.cmdline import CmdLineHandler
+
 from .coldcard import ColdcardPlugin
 
 
 _logger = get_logger(__name__)
 
 
-class ColdcardCmdLineHandler:
+class ColdcardCmdLineHandler(CmdLineHandler):
 
     def get_passphrase(self, msg, confirm):
         raise NotImplementedError
diff --git a/electrum/plugins/hw_wallet/__init__.py b/electrum/plugins/hw_wallet/__init__.py
index 6e3ce1a00..8fd806783 100644
--- a/electrum/plugins/hw_wallet/__init__.py
+++ b/electrum/plugins/hw_wallet/__init__.py
@@ -1,2 +1,2 @@
-from .plugin import HW_PluginBase, HardwareClientBase
+from .plugin import HW_PluginBase, HardwareClientBase, HardwareHandlerBase
 from .cmdline import CmdLineHandler
diff --git a/electrum/plugins/hw_wallet/cmdline.py b/electrum/plugins/hw_wallet/cmdline.py
index b91e094b8..5210267f1 100644
--- a/electrum/plugins/hw_wallet/cmdline.py
+++ b/electrum/plugins/hw_wallet/cmdline.py
@@ -1,11 +1,13 @@
 from electrum.util import print_stderr, raw_input
 from electrum.logging import get_logger
 
+from .plugin import HardwareHandlerBase
+
 
 _logger = get_logger(__name__)
 
 
-class CmdLineHandler:
+class CmdLineHandler(HardwareHandlerBase):
 
     def get_passphrase(self, msg, confirm):
         import getpass
diff --git a/electrum/plugins/hw_wallet/plugin.py b/electrum/plugins/hw_wallet/plugin.py
index 97201f40e..61129601d 100644
--- a/electrum/plugins/hw_wallet/plugin.py
+++ b/electrum/plugins/hw_wallet/plugin.py
@@ -37,6 +37,7 @@ from electrum.keystore import Xpub, Hardware_KeyStore
 
 if TYPE_CHECKING:
     from electrum.wallet import Abstract_Wallet
+    from electrum.base_wizard import BaseWizard
 
 
 class HW_PluginBase(BasePlugin):
@@ -63,7 +64,7 @@ class HW_PluginBase(BasePlugin):
             if isinstance(keystore, self.keystore_class):
                 self.device_manager().unpair_xpub(keystore.xpub)
 
-    def setup_device(self, device_info, wizard, purpose):
+    def setup_device(self, device_info, wizard: 'BaseWizard', purpose):
         """Called when creating a new wallet or when using the device to decrypt
         an existing wallet. Select the device to use.  If the device is
         uninitialized, go through the initialization process.
@@ -139,15 +140,23 @@ class HW_PluginBase(BasePlugin):
     def is_outdated_fw_ignored(self) -> bool:
         return self._ignore_outdated_fw
 
-    def create_client(self, device: 'Device', handler) -> Optional['HardwareClientBase']:
+    def create_client(self, device: 'Device',
+                      handler: Optional['HardwareHandlerBase']) -> Optional['HardwareClientBase']:
         raise NotImplementedError()
 
-    def get_xpub(self, device_id, derivation: str, xtype, wizard) -> str:
+    def get_xpub(self, device_id, derivation: str, xtype, wizard: 'BaseWizard') -> str:
+        raise NotImplementedError()
+
+    def create_handler(self, window) -> 'HardwareHandlerBase':
+        # note: in Qt GUI, 'window' is either an ElectrumWindow or an InstallWizard
         raise NotImplementedError()
 
 
 class HardwareClientBase:
 
+    plugin: 'HW_PluginBase'
+    handler: Optional['HardwareHandlerBase']
+
     def is_pairable(self) -> bool:
         raise NotImplementedError()
 
@@ -191,6 +200,41 @@ class HardwareClientBase:
         return password
 
 
+class HardwareHandlerBase:
+    """An interface between the GUI and the device handling logic for handling I/O."""
+    win = None
+    device: str
+
+    def get_wallet(self) -> Optional['Abstract_Wallet']:
+        if self.win is not None:
+            if hasattr(self.win, 'wallet'):
+                return self.win.wallet
+
+    def update_status(self, paired: bool) -> None:
+        pass
+
+    def query_choice(self, msg: str, labels: Sequence[str]) -> Optional[int]:
+        raise NotImplementedError()
+
+    def yes_no_question(self, msg: str) -> bool:
+        raise NotImplementedError()
+
+    def show_message(self, msg: str, on_cancel=None) -> None:
+        raise NotImplementedError()
+
+    def show_error(self, msg: str, blocking: bool = False) -> None:
+        raise NotImplementedError()
+
+    def finished(self) -> None:
+        pass
+
+    def get_word(self, msg: str) -> str:
+        raise NotImplementedError()
+
+    def get_passphrase(self, msg: str, confirm: bool) -> Optional[str]:
+        raise NotImplementedError()
+
+
 def is_any_tx_output_on_change_branch(tx: PartialTransaction) -> bool:
     return any([txout.is_change for txout in tx.outputs()])
 
diff --git a/electrum/plugins/hw_wallet/qt.py b/electrum/plugins/hw_wallet/qt.py
index 4dbd2ac15..309e05783 100644
--- a/electrum/plugins/hw_wallet/qt.py
+++ b/electrum/plugins/hw_wallet/qt.py
@@ -35,13 +35,14 @@ from electrum.gui.qt.password_dialog import PasswordLayout, PW_PASSPHRASE
 from electrum.gui.qt.util import (read_QIcon, WWLabel, OkButton, WindowModalDialog,
                                   Buttons, CancelButton, TaskThread, char_width_in_lineedit)
 from electrum.gui.qt.main_window import StatusBarButton, ElectrumWindow
+from electrum.gui.qt.installwizard import InstallWizard
 
 from electrum.i18n import _
 from electrum.logging import Logger
 from electrum.util import parse_URI, InvalidBitcoinURI, UserCancelled
 from electrum.plugin import hook, DeviceUnpairableError
 
-from .plugin import OutdatedHwFirmwareException, HW_PluginBase
+from .plugin import OutdatedHwFirmwareException, HW_PluginBase, HardwareHandlerBase
 
 if TYPE_CHECKING:
     from electrum.wallet import Abstract_Wallet
@@ -50,7 +51,7 @@ if TYPE_CHECKING:
 
 # The trickiest thing about this handler was getting windows properly
 # parented on macOS.
-class QtHandlerBase(QObject, Logger):
+class QtHandlerBase(HardwareHandlerBase, QObject, Logger):
     '''An interface between the GUI (here, QT) and the device handling
     logic for handling I/O.'''
 
@@ -63,7 +64,7 @@ class QtHandlerBase(QObject, Logger):
     yes_no_signal = pyqtSignal(object)
     status_signal = pyqtSignal(object)
 
-    def __init__(self, win, device):
+    def __init__(self, win: Union[ElectrumWindow, InstallWizard], device: str):
         QObject.__init__(self)
         Logger.__init__(self)
         self.clear_signal.connect(self.clear_dialog)
@@ -267,5 +268,5 @@ class QtPluginBase(object):
         dev_name = f"{plugin.device} ({keystore.label})"
         receive_address_e.addButton("eye1.png", show_address, _("Show on {}").format(dev_name))
 
-    def create_handler(self, window: ElectrumWindow) -> 'QtHandlerBase':
+    def create_handler(self, window: Union[ElectrumWindow, InstallWizard]) -> 'QtHandlerBase':
         raise NotImplementedError()
diff --git a/electrum/plugins/keepkey/keepkey.py b/electrum/plugins/keepkey/keepkey.py
index 3a1c31c4b..e035307f9 100644
--- a/electrum/plugins/keepkey/keepkey.py
+++ b/electrum/plugins/keepkey/keepkey.py
@@ -282,7 +282,6 @@ class KeepKeyPlugin(HW_PluginBase):
         if client is None:
             raise UserFacingException(_('Failed to create a client for this device.') + '\n' +
                                       _('Make sure it is in the correct state.'))
-        # fixme: we should use: client.handler = wizard
         client.handler = self.create_handler(wizard)
         if not device_info.initialized:
             self.initialize_device(device_id, wizard, client.handler)
@@ -294,7 +293,7 @@ class KeepKeyPlugin(HW_PluginBase):
             raise ScriptTypeNotSupported(_('This type of script is not supported with {}.').format(self.device))
         devmgr = self.device_manager()
         client = devmgr.client_by_id(device_id)
-        client.handler = wizard
+        client.handler = self.create_handler(wizard)
         xpub = client.get_xpub(derivation, xtype)
         client.used()
         return xpub
diff --git a/electrum/plugins/keepkey/qt.py b/electrum/plugins/keepkey/qt.py
index eb6f0cb63..fce633df9 100644
--- a/electrum/plugins/keepkey/qt.py
+++ b/electrum/plugins/keepkey/qt.py
@@ -195,9 +195,6 @@ class QtPlugin(QtPluginBase):
     #   icon_file
     #   pin_matrix_widget_class
 
-    def create_handler(self, window):
-        return QtHandler(window, self.pin_matrix_widget_class(), self.device)
-
     @only_hook_if_libraries_available
     @hook
     def receive_menu(self, menu, addrs, wallet):
@@ -302,6 +299,9 @@ class Plugin(KeepKeyPlugin, QtPlugin):
     icon_paired = "keepkey.png"
     icon_unpaired = "keepkey_unpaired.png"
 
+    def create_handler(self, window):
+        return QtHandler(window, self.pin_matrix_widget_class(), self.device)
+
     @classmethod
     def pin_matrix_widget_class(self):
         from keepkeylib.qt.pinmatrix import PinMatrixWidget
diff --git a/electrum/plugins/safe_t/qt.py b/electrum/plugins/safe_t/qt.py
index 224eec802..aa44495bb 100644
--- a/electrum/plugins/safe_t/qt.py
+++ b/electrum/plugins/safe_t/qt.py
@@ -71,9 +71,6 @@ class QtPlugin(QtPluginBase):
     #   icon_file
     #   pin_matrix_widget_class
 
-    def create_handler(self, window):
-        return QtHandler(window, self.pin_matrix_widget_class(), self.device)
-
     @only_hook_if_libraries_available
     @hook
     def receive_menu(self, menu, addrs, wallet):
@@ -176,6 +173,9 @@ class Plugin(SafeTPlugin, QtPlugin):
     icon_unpaired = "safe-t_unpaired.png"
     icon_paired = "safe-t.png"
 
+    def create_handler(self, window):
+        return QtHandler(window, self.pin_matrix_widget_class(), self.device)
+
     @classmethod
     def pin_matrix_widget_class(self):
         from safetlib.qt.pinmatrix import PinMatrixWidget
diff --git a/electrum/plugins/safe_t/safe_t.py b/electrum/plugins/safe_t/safe_t.py
index 8c10bf293..22064094c 100644
--- a/electrum/plugins/safe_t/safe_t.py
+++ b/electrum/plugins/safe_t/safe_t.py
@@ -256,7 +256,6 @@ class SafeTPlugin(HW_PluginBase):
         if client is None:
             raise UserFacingException(_('Failed to create a client for this device.') + '\n' +
                                       _('Make sure it is in the correct state.'))
-        # fixme: we should use: client.handler = wizard
         client.handler = self.create_handler(wizard)
         if not device_info.initialized:
             self.initialize_device(device_id, wizard, client.handler)
@@ -268,7 +267,7 @@ class SafeTPlugin(HW_PluginBase):
             raise ScriptTypeNotSupported(_('This type of script is not supported with {}.').format(self.device))
         devmgr = self.device_manager()
         client = devmgr.client_by_id(device_id)
-        client.handler = wizard
+        client.handler = self.create_handler(wizard)
         xpub = client.get_xpub(derivation, xtype)
         client.used()
         return xpub
diff --git a/electrum/plugins/trezor/qt.py b/electrum/plugins/trezor/qt.py
index 3a8b2cba3..37a45ce6b 100644
--- a/electrum/plugins/trezor/qt.py
+++ b/electrum/plugins/trezor/qt.py
@@ -169,9 +169,6 @@ class QtPlugin(QtPluginBase):
     #   icon_file
     #   pin_matrix_widget_class
 
-    def create_handler(self, window):
-        return QtHandler(window, self.pin_matrix_widget_class(), self.device)
-
     @only_hook_if_libraries_available
     @hook
     def receive_menu(self, menu, addrs, wallet):
@@ -377,6 +374,9 @@ class Plugin(TrezorPlugin, QtPlugin):
     icon_unpaired = "trezor_unpaired.png"
     icon_paired = "trezor.png"
 
+    def create_handler(self, window):
+        return QtHandler(window, self.pin_matrix_widget_class(), self.device)
+
     @classmethod
     def pin_matrix_widget_class(self):
         from trezorlib.qt.pinmatrix import PinMatrixWidget
diff --git a/electrum/plugins/trezor/trezor.py b/electrum/plugins/trezor/trezor.py
index 71341d91c..d1d94b010 100644
--- a/electrum/plugins/trezor/trezor.py
+++ b/electrum/plugins/trezor/trezor.py
@@ -282,7 +282,6 @@ class TrezorPlugin(HW_PluginBase):
                    .format(self.device, client.label(), self.firmware_URL))
             raise OutdatedHwFirmwareException(msg)
 
-        # fixme: we should use: client.handler = wizard
         client.handler = self.create_handler(wizard)
         if not device_info.initialized:
             self.initialize_device(device_id, wizard, client.handler)
@@ -295,7 +294,7 @@ class TrezorPlugin(HW_PluginBase):
             raise ScriptTypeNotSupported(_('This type of script is not supported with {}.').format(self.device))
         devmgr = self.device_manager()
         client = devmgr.client_by_id(device_id)
-        client.handler = wizard
+        client.handler = self.create_handler(wizard)
         xpub = client.get_xpub(derivation, xtype)
         client.used()
         return xpub