diff --git a/electrum/gui/qt/confirm_tx_dialog.py b/electrum/gui/qt/confirm_tx_dialog.py
index 8a9297b28..1f7a5aa4d 100644
--- a/electrum/gui/qt/confirm_tx_dialog.py
+++ b/electrum/gui/qt/confirm_tx_dialog.py
@@ -421,6 +421,8 @@ class TxEditor(WindowModalDialog):
                 _('This may result in higher transactions fees.')
             ]))
         self.use_multi_change_menu.setEnabled(self.wallet.use_change)
+        # fixme: some of these options (WALLET_SEND_CHANGE_TO_LIGHTNING, WALLET_MERGE_DUPLICATE_OUTPUTS)
+        # only make sense when we create a new tx, and should not be visible/enabled in rbf dialog
         add_cv_action(self.config.cv.WALLET_MERGE_DUPLICATE_OUTPUTS, self.toggle_merge_duplicate_outputs)
         add_cv_action(self.config.cv.WALLET_SPEND_CONFIRMED_ONLY, self.toggle_confirmed_only)
         add_cv_action(self.config.cv.WALLET_COIN_CHOOSER_OUTPUT_ROUNDING, self.toggle_output_rounding)
diff --git a/electrum/gui/qt/send_tab.py b/electrum/gui/qt/send_tab.py
index 7fc6833b1..4b6064ffc 100644
--- a/electrum/gui/qt/send_tab.py
+++ b/electrum/gui/qt/send_tab.py
@@ -322,6 +322,7 @@ class SendTab(QWidget, MessageBoxMixin, Logger):
                 base_tx=base_tx,
                 is_sweep=is_sweep,
                 send_change_to_lightning=self.config.WALLET_SEND_CHANGE_TO_LIGHTNING,
+                merge_duplicate_outputs=self.config.WALLET_MERGE_DUPLICATE_OUTPUTS,
             )
         output_values = [x.value for x in outputs]
         is_max = any(parse_max_spend(outval) for outval in output_values)
diff --git a/electrum/wallet.py b/electrum/wallet.py
index 46758ea8d..e1875bb05 100644
--- a/electrum/wallet.py
+++ b/electrum/wallet.py
@@ -1828,6 +1828,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
             BIP69_sort: Optional[bool] = True,
             base_tx: Optional[PartialTransaction] = None,
             send_change_to_lightning: bool = False,
+            merge_duplicate_outputs: bool = False,
     ) -> PartialTransaction:
         """Can raise NotEnoughFunds or NoDynamicFeeEstimates."""
 
@@ -1900,7 +1901,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
                 old_change_addrs = []
             # change address. if empty, coin_chooser will set it
             change_addrs = self.get_change_addresses_for_new_transaction(change_addr or old_change_addrs)
-            if self.config.WALLET_MERGE_DUPLICATE_OUTPUTS:
+            if merge_duplicate_outputs:
                 txo = transaction.merge_duplicate_tx_outputs(txo)
             tx = coin_chooser.make_tx(
                 coins=coins,
@@ -3083,6 +3084,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
             base_tx: Optional[PartialTransaction] = None,
             inputs: Optional[List[PartialTxInput]] = None,
             send_change_to_lightning: Optional[bool] = None,
+            merge_duplicate_outputs: Optional[bool] = None,
             nonlocal_only: bool = False,
             BIP69_sort: bool = True,
     ) -> PartialTransaction:
@@ -3098,6 +3100,7 @@ class Abstract_Wallet(ABC, Logger, EventListener):
             change_addr=change_addr,
             base_tx=base_tx,
             send_change_to_lightning=send_change_to_lightning,
+            merge_duplicate_outputs=merge_duplicate_outputs,
             rbf=rbf,
             BIP69_sort=BIP69_sort,
         )
diff --git a/tests/test_wallet_vertical.py b/tests/test_wallet_vertical.py
index f3b1d9a36..028b7525c 100644
--- a/tests/test_wallet_vertical.py
+++ b/tests/test_wallet_vertical.py
@@ -2062,11 +2062,10 @@ class TestWalletSending(ElectrumTestCase):
         wallet.adb.receive_tx_callback(tx1, TX_HEIGHT_UNCONFIRMED)
         self.assertEqual((0, 298_000, 0), wallet.get_balance())
 
-        wallet.config.WALLET_MERGE_DUPLICATE_OUTPUTS = True
         # second payment to dest_addr  (merged)
         outputs2 = [PartialTxOutput.from_address_and_value(dest_addr, 100_000)]
         coins = wallet.get_spendable_coins(domain=None)
-        tx2 = wallet.make_unsigned_transaction(coins=coins, outputs=outputs2, fee_policy=FixedFeePolicy(3000), base_tx=tx1)
+        tx2 = wallet.make_unsigned_transaction(coins=coins, outputs=outputs2, fee_policy=FixedFeePolicy(3000), base_tx=tx1, merge_duplicate_outputs=True)
         tx2.set_rbf(True)
         tx2.locktime = 2534850
         tx2.version = 2
@@ -2081,7 +2080,6 @@ class TestWalletSending(ElectrumTestCase):
         wallet.adb.receive_tx_callback(tx1, TX_HEIGHT_UNCONFIRMED)
         self.assertEqual((0, 298_000, 0), wallet.get_balance())
 
-        wallet.config.WALLET_MERGE_DUPLICATE_OUTPUTS = False
         # second payment to dest_addr  (not merged, just duplicate outputs)
         outputs2 = [PartialTxOutput.from_address_and_value(dest_addr, 100_000)]
         coins = wallet.get_spendable_coins(domain=None)