diff --git a/electrum/gui/qt/send_tab.py b/electrum/gui/qt/send_tab.py
index 1fe77717f..3385c7dbc 100644
--- a/electrum/gui/qt/send_tab.py
+++ b/electrum/gui/qt/send_tab.py
@@ -313,7 +313,7 @@ class SendTab(QWidget, MessageBoxMixin, Logger):
         if get_coins is None:
             get_coins = self.window.get_coins
 
-        def make_tx(fee_policy, *, confirmed_only=False, base_tx=False):
+        def make_tx(fee_policy, *, confirmed_only=False, base_tx=None):
             coins = get_coins(nonlocal_only=nonlocal_only, confirmed_only=confirmed_only)
             return self.wallet.make_unsigned_transaction(
                 fee_policy=fee_policy,