diff --git a/electrum/descriptor.py b/electrum/descriptor.py
index 3a278c45e..fcf2dd664 100644
--- a/electrum/descriptor.py
+++ b/electrum/descriptor.py
@@ -1031,6 +1031,9 @@ def parse_descriptor(desc: str) -> 'Descriptor':
 #####
 
 
+class NotLegacySinglesigScriptType(Exception): pass
+
+
 def get_singlesig_descriptor_from_legacy_leaf(*, pubkey: str, script_type: str) -> Optional[Descriptor]:
     pubkey = PubkeyProvider.parse(pubkey)
     if script_type == 'p2pk':
@@ -1043,7 +1046,7 @@ def get_singlesig_descriptor_from_legacy_leaf(*, pubkey: str, script_type: str)
         wpkh = WPKHDescriptor(pubkey=pubkey)
         return SHDescriptor(subdescriptor=wpkh)
     else:
-        raise NotImplementedError(f"unexpected {script_type=}")
+        raise NotLegacySinglesigScriptType(f"unexpected {script_type=}")
 
 
 def create_dummy_descriptor_from_address(addr: Optional[str]) -> 'Descriptor':
diff --git a/electrum/gui/qml/qetxfinalizer.py b/electrum/gui/qml/qetxfinalizer.py
index accbcfb1e..368d0c6cd 100644
--- a/electrum/gui/qml/qetxfinalizer.py
+++ b/electrum/gui/qml/qetxfinalizer.py
@@ -999,6 +999,7 @@ class QETxSweepFinalizer(QETxFinalizer):
     def make_sweep_tx(self):
         address = self._wallet.wallet.get_receiving_address()
         assert self._wallet.wallet.is_mine(address)
+        assert self._txins is not None
 
         coins, keypairs = copy.deepcopy(self._txins)
         outputs = [PartialTxOutput.from_address_and_value(address, value='!')]
@@ -1033,6 +1034,9 @@ class QETxSweepFinalizer(QETxFinalizer):
         if not self._private_keys:
             self._logger.debug('private keys not set, ignoring update()')
             return
+        if self._txins is None:
+            self._logger.debug('txins not set, ignoring update()')
+            return
 
         try:
             # make unsigned transaction
diff --git a/electrum/wallet.py b/electrum/wallet.py
index 17c8be3c9..894c3a963 100644
--- a/electrum/wallet.py
+++ b/electrum/wallet.py
@@ -137,7 +137,10 @@ async def sweep_preparations(
 
     async def find_utxos_for_privkey(txin_type: str, privkey: bytes, compressed: bool):
         pubkey = ecc.ECPrivkey(privkey).get_public_key_bytes(compressed=compressed)
-        desc = descriptor.get_singlesig_descriptor_from_legacy_leaf(pubkey=pubkey.hex(), script_type=txin_type)
+        try:
+            desc = descriptor.get_singlesig_descriptor_from_legacy_leaf(pubkey=pubkey.hex(), script_type=txin_type)
+        except descriptor.NotLegacySinglesigScriptType:
+            raise UserFacingException(_("Unsupported script-type ({}) for sweeping.").format(txin_type)) from None
         await _append_utxos_to_inputs(
             inputs=inputs,
             network=network,
@@ -3710,7 +3713,7 @@ class Imported_Wallet(Simple_Wallet):
                 for txin_type in bitcoin.WIF_SCRIPT_TYPES.keys():
                     try:
                         addr2 = bitcoin.pubkey_to_address(txin_type, pubkey)
-                    except NotImplementedError:
+                    except descriptor.NotLegacySinglesigScriptType:
                         pass
                     else:
                         if self.db.has_imported_address(addr2):