diff --git a/electrum/gui/kivy/uix/dialogs/invoice_dialog.py b/electrum/gui/kivy/uix/dialogs/invoice_dialog.py
index f64471e02..a694c1979 100644
--- a/electrum/gui/kivy/uix/dialogs/invoice_dialog.py
+++ b/electrum/gui/kivy/uix/dialogs/invoice_dialog.py
@@ -1,3 +1,5 @@
+from typing import TYPE_CHECKING
+
 from kivy.factory import Factory
 from kivy.lang import Builder
 from kivy.core.clipboard import Clipboard
@@ -7,6 +9,9 @@ from kivy.clock import Clock
 from electrum.gui.kivy.i18n import _
 from electrum.util import pr_tooltips
 
+if TYPE_CHECKING:
+    from electrum.gui.kivy.main_window import ElectrumWindow
+
 
 Builder.load_string('''
 <InvoiceDialog@Popup>
@@ -58,7 +63,7 @@ class InvoiceDialog(Factory.Popup):
 
     def __init__(self, title, data, key):
         Factory.Popup.__init__(self)
-        self.app = App.get_running_app()
+        self.app = App.get_running_app()  # type: ElectrumWindow
         self.title = title
         self.data = data
         self.key = key
diff --git a/electrum/gui/kivy/uix/screens.py b/electrum/gui/kivy/uix/screens.py
index bb5417f76..556f80b50 100644
--- a/electrum/gui/kivy/uix/screens.py
+++ b/electrum/gui/kivy/uix/screens.py
@@ -4,6 +4,7 @@ from decimal import Decimal
 import re
 import threading
 import traceback, sys
+from typing import TYPE_CHECKING, List
 
 from kivy.app import App
 from kivy.cache import Cache
@@ -39,6 +40,9 @@ from .dialogs.lightning_open_channel import LightningOpenChannelDialog
 
 from electrum.gui.kivy.i18n import _
 
+if TYPE_CHECKING:
+    from electrum.gui.kivy.main_window import ElectrumWindow
+
 
 class HistoryRecycleView(RecycleView):
     pass
@@ -54,7 +58,7 @@ class CScreen(Factory.Screen):
     action_view = ObjectProperty(None)
     loaded = False
     kvname = None
-    app = App.get_running_app()
+    app = App.get_running_app()  # type: ElectrumWindow
 
     def _change_action_view(self):
         app = App.get_running_app()
@@ -310,7 +314,7 @@ class SendScreen(CScreen):
             if not bitcoin.is_address(address):
                 self.app.show_error(_('Invalid Bitcoin Address') + ':\n' + address)
                 return
-            outputs = [(TYPE_ADDRESS, address, amount)]
+            outputs = [TxOutput(TYPE_ADDRESS, address, amount)]
             return self.app.wallet.create_invoice(outputs, message, self.payment_request, self.parsed_URI)
 
     def do_save(self):
@@ -336,8 +340,8 @@ class SendScreen(CScreen):
             return
         elif invoice['type'] == PR_TYPE_ONCHAIN:
             message = invoice['message']
-            outputs = invoice['outputs']
-            amount = sum(map(lambda x:x[2], outputs))
+            outputs = invoice['outputs']  # type: List[TxOutput]
+            amount = sum(map(lambda x: x.value, outputs))
             do_pay = lambda rbf: self._do_send_onchain(amount, message, outputs, rbf)
             if self.app.electrum_config.get('use_rbf'):
                 d = Question(_('Should this transaction be replaceable?'), do_pay)
diff --git a/electrum/paymentrequest.py b/electrum/paymentrequest.py
index 286db43e1..293ad3d03 100644
--- a/electrum/paymentrequest.py
+++ b/electrum/paymentrequest.py
@@ -248,7 +248,7 @@ class PaymentRequest:
         return self.details.expires
 
     def get_amount(self):
-        return sum(map(lambda x:x[2], self.outputs))
+        return sum(map(lambda x:x.value, self.outputs))
 
     def get_address(self):
         o = self.outputs[0]
diff --git a/electrum/wallet.py b/electrum/wallet.py
index 8990244b0..8a14d28a8 100644
--- a/electrum/wallet.py
+++ b/electrum/wallet.py
@@ -228,6 +228,12 @@ class Abstract_Wallet(AddressSynchronizer):
         self.receive_requests      = storage.get('payment_requests', {})
         self.invoices              = storage.get('invoices', {})
 
+        # convert invoices
+        for invoice_key, invoice in self.invoices.items():
+            if invoice['type'] == PR_TYPE_ONCHAIN:
+                outputs = [TxOutput(*output) for output in invoice.get('outputs')]
+                invoice['outputs'] = outputs
+
         self.calc_unused_change_addresses()
 
         # save wallet type the first time