diff --git a/electrum/gui/qml/qetxfinalizer.py b/electrum/gui/qml/qetxfinalizer.py
index bafe4a6c4..1b378d608 100644
--- a/electrum/gui/qml/qetxfinalizer.py
+++ b/electrum/gui/qml/qetxfinalizer.py
@@ -434,7 +434,10 @@ class QETxFinalizer(TxFeeSlider):
         self.update_fee_warning_from_tx(tx=tx, invoice_amt=amount)
 
         if self._amount.isMax and not self.warning:
-            if reserve_sats := sum(txo.value for txo in tx.outputs() if txo.is_utxo_reserve):
+            if reserve_sats := self._wallet.wallet.tx_keeps_ln_utxo_reserve(
+                tx,
+                gui_spend_max=self._amount.isMax
+            ):
                 reserve_str = self._config.format_amount_and_units(reserve_sats)
                 self.warning = ' '.join([
                     _('Warning') + ':',
diff --git a/electrum/gui/qt/confirm_tx_dialog.py b/electrum/gui/qt/confirm_tx_dialog.py
index b18f8332b..6ab873331 100644
--- a/electrum/gui/qt/confirm_tx_dialog.py
+++ b/electrum/gui/qt/confirm_tx_dialog.py
@@ -544,7 +544,7 @@ class TxEditor(WindowModalDialog):
         if any((txin.block_height is not None and txin.block_height<=0) for txin in self.tx.inputs()):
             messages.append(_('This transaction will spend unconfirmed coins.'))
         # warn if a reserve utxo was added
-        if reserve_sats := sum(txo.value for txo in self.tx.outputs() if txo.is_utxo_reserve):
+        if reserve_sats := self.wallet.tx_keeps_ln_utxo_reserve(self.tx, gui_spend_max=bool(self.output_value == '!')):
             reserve_str = self.main_window.config.format_amount_and_units(reserve_sats)
             messages.append(_('Could not spend max: a security reserve of {} was kept for your Lightning channels.').format(reserve_str))
         # warn if we merge from mempool
diff --git a/electrum/wallet.py b/electrum/wallet.py
index 37c05e742..efdcf03e9 100644
--- a/electrum/wallet.py
+++ b/electrum/wallet.py
@@ -1911,6 +1911,19 @@ class Abstract_Wallet(ABC, Logger, EventListener):
     def is_low_reserve(self) -> bool:
         return self.should_keep_reserve_utxo([], [], False)
 
+    def tx_keeps_ln_utxo_reserve(self, tx, *, gui_spend_max: bool) -> Optional[int]:
+        if reserve_output_amount := sum(txo.value for txo in tx.outputs() if txo.is_utxo_reserve):
+            # tx has a reserve change output
+            return reserve_output_amount
+        if gui_spend_max:  # user tried to spend max amount
+            coins_in_wallet = self.get_spendable_coins(nonlocal_only=False, confirmed_only=False)
+            amount_in_wallet = sum(c.value_sats() for c in coins_in_wallet)
+            tx_spend_amount = tx.output_value() + tx.get_fee()
+            if amount_in_wallet - tx_spend_amount == self.config.LN_UTXO_RESERVE:
+                # tx keeps exactly LN_UTXO_RESERVE amount sats in the wallet
+                return self.config.LN_UTXO_RESERVE
+        return None
+
     @profiler(min_threshold=0.1)
     def make_unsigned_transaction(
             self, *,