diff --git a/electrum/gui/qt/confirm_tx_dialog.py b/electrum/gui/qt/confirm_tx_dialog.py
index 6e1091137..ea937a51b 100644
--- a/electrum/gui/qt/confirm_tx_dialog.py
+++ b/electrum/gui/qt/confirm_tx_dialog.py
@@ -80,7 +80,7 @@ class TxEditor:
     def get_fee_estimator(self):
         return None
 
-    def update_tx(self):
+    def update_tx(self, *, fallback_to_zero_fee: bool = False):
         fee_estimator = self.get_fee_estimator()
         try:
             self.tx = self.make_tx(fee_estimator)
@@ -89,7 +89,13 @@ class TxEditor:
         except NotEnoughFunds:
             self.not_enough_funds = True
             self.tx = None
-            return
+            if fallback_to_zero_fee:
+                try:
+                    self.tx = self.make_tx(0)
+                except BaseException:
+                    return
+            else:
+                return
         except NoDynamicFeeEstimates:
             self.no_dynfee_estimates = True
             self.tx = None
diff --git a/electrum/gui/qt/transaction_dialog.py b/electrum/gui/qt/transaction_dialog.py
index 09301c00a..c84ad4836 100644
--- a/electrum/gui/qt/transaction_dialog.py
+++ b/electrum/gui/qt/transaction_dialog.py
@@ -393,7 +393,7 @@ class BaseTxDialog(QDialog, MessageBoxMixin):
     def update(self):
         if not self.finalized:
             self.update_fee_fields()
-            self.finalize_button.setEnabled(self.tx is not None)
+            self.finalize_button.setEnabled(self.can_finalize())
         if self.tx is None:
             return
         self.update_io()
@@ -659,6 +659,9 @@ class BaseTxDialog(QDialog, MessageBoxMixin):
     def set_title(self):
         self.setWindowTitle(_("Create transaction") if not self.finalized else _("Transaction"))
 
+    def can_finalize(self) -> bool:
+        return False
+
     def on_finalize(self):
         pass  # overridden in subclass
 
@@ -688,7 +691,8 @@ class PreviewTxDialog(BaseTxDialog, TxEditor):
         TxEditor.__init__(self, window=window, make_tx=make_tx, is_sweep=bool(external_keypairs))
         BaseTxDialog.__init__(self, parent=window, desc='', prompt_if_unsaved=False,
                               finalized=False, external_keypairs=external_keypairs)
-        BlockingWaitingDialog(window, _("Preparing transaction..."), self.update_tx)
+        BlockingWaitingDialog(window, _("Preparing transaction..."),
+                              lambda: self.update_tx(fallback_to_zero_fee=True))
         self.update()
 
     def create_fee_controls(self):
@@ -861,9 +865,14 @@ class PreviewTxDialog(BaseTxDialog, TxEditor):
         self.feerounding_icon.setToolTip(self.feerounding_text)
         self.feerounding_icon.setVisible(abs(feerounding) >= 1)
 
+    def can_finalize(self):
+        return (self.tx is not None
+                and not self.not_enough_funds)
+
     def on_finalize(self):
-        if not self.tx:
+        if not self.can_finalize():
             return
+        assert self.tx
         self.finalized = True
         self.tx.set_rbf(self.rbf_cb.isChecked())
         self.tx.locktime = self.locktime_e.get_locktime()