diff --git a/electrum/address_synchronizer.py b/electrum/address_synchronizer.py
index ab32ccbb0..3af00368c 100644
--- a/electrum/address_synchronizer.py
+++ b/electrum/address_synchronizer.py
@@ -216,7 +216,8 @@ class AddressSynchronizer(Logger):
     def add_transaction(self, tx: Transaction, *, allow_unrelated=False) -> bool:
         """Returns whether the tx was successfully added to the wallet history."""
         assert tx, tx
-        assert tx.is_complete()
+        # note: tx.is_complete() is not necessarily True; tx might be partial
+        # but it *needs* to have a txid:
         tx_hash = tx.txid()
         if tx_hash is None:
             raise Exception("cannot add tx without txid to wallet history")
diff --git a/electrum/gui/qt/transaction_dialog.py b/electrum/gui/qt/transaction_dialog.py
index 3b1d85989..d9a4af73c 100644
--- a/electrum/gui/qt/transaction_dialog.py
+++ b/electrum/gui/qt/transaction_dialog.py
@@ -281,7 +281,6 @@ class BaseTxDialog(QDialog, MessageBoxMixin):
 
     def sign(self):
         def sign_done(success):
-            # note: with segwit we could save partially signed tx, because they have a txid
             if self.tx.is_complete():
                 self.prompt_if_unsaved = True
                 self.saved = False
diff --git a/electrum/json_db.py b/electrum/json_db.py
index 3a1519f1b..8b7239201 100644
--- a/electrum/json_db.py
+++ b/electrum/json_db.py
@@ -33,7 +33,7 @@ from typing import Dict, Optional, List, Tuple, Set, Iterable, NamedTuple, Seque
 from . import util, bitcoin
 from .util import profiler, WalletFileException, multisig_type, TxMinedInfo, bfh
 from .keystore import bip44_derivation
-from .transaction import Transaction, TxOutpoint
+from .transaction import Transaction, TxOutpoint, tx_from_any
 from .logging import Logger
 
 # seed_version is now used for the version of the wallet file
@@ -700,8 +700,16 @@ class JsonDB(Logger):
 
     @modifier
     def add_transaction(self, tx_hash: str, tx: Transaction) -> None:
-        assert isinstance(tx, Transaction)
-        self.transactions[tx_hash] = tx
+        assert isinstance(tx, Transaction), tx
+        # note that tx might be a PartialTransaction
+        if not tx_hash:
+            raise Exception("trying to add tx to db without txid")
+        if tx_hash != tx.txid():
+            raise Exception(f"trying to add tx to db with inconsistent txid: {tx_hash} != {tx.txid()}")
+        # don't allow overwriting complete tx with partial tx
+        tx_we_already_have = self.transactions.get(tx_hash, None)
+        if tx_we_already_have is None or not tx_we_already_have.is_complete():
+            self.transactions[tx_hash] = tx
 
     @modifier
     def remove_transaction(self, tx_hash) -> Optional[Transaction]:
@@ -903,9 +911,9 @@ class JsonDB(Logger):
         self.tx_fees = self.get_data_ref('tx_fees')  # type: Dict[str, TxFeesValue]
         # scripthash -> set of (outpoint, value)
         self._prevouts_by_scripthash = self.get_data_ref('prevouts_by_scripthash')  # type: Dict[str, Set[Tuple[str, int]]]
-        # convert raw hex transactions to Transaction objects
+        # convert raw transactions to Transaction objects
         for tx_hash, raw_tx in self.transactions.items():
-            self.transactions[tx_hash] = Transaction(raw_tx)
+            self.transactions[tx_hash] = tx_from_any(raw_tx)
         # convert txi, txo: list to set
         for t in self.txi, self.txo:
             for d in t.values():
diff --git a/electrum/wallet.py b/electrum/wallet.py
index dc6dd7d76..88017db9b 100644
--- a/electrum/wallet.py
+++ b/electrum/wallet.py
@@ -353,7 +353,9 @@ class Abstract_Wallet(AddressSynchronizer):
     def is_deterministic(self):
         return self.keystore.is_deterministic()
 
-    def set_label(self, name, text = None):
+    def set_label(self, name: str, text: str = None) -> bool:
+        if not name:
+            return False
         changed = False
         old_text = self.labels.get(name)
         if text:
@@ -469,12 +471,14 @@ class Abstract_Wallet(AddressSynchronizer):
         exp_n = None
         can_broadcast = False
         can_bump = False
-        can_save_as_local = False
-        label = ''
         tx_hash = tx.txid()
+        tx_we_already_have_in_db = self.db.get_transaction(tx_hash)
+        can_save_as_local = (is_relevant and tx.txid() is not None
+                             and (tx_we_already_have_in_db is None or not tx_we_already_have_in_db.is_complete()))
+        label = ''
         tx_mined_status = self.get_tx_height(tx_hash)
         if tx.is_complete():
-            if self.db.get_transaction(tx_hash):
+            if tx_we_already_have_in_db:
                 label = self.get_label(tx_hash)
                 if tx_mined_status.height > 0:
                     if tx_mined_status.conf:
@@ -497,7 +501,6 @@ class Abstract_Wallet(AddressSynchronizer):
             else:
                 status = _("Signed")
                 can_broadcast = self.network is not None
-                can_save_as_local = is_relevant
         else:
             s, r = tx.signature_count()
             status = _("Unsigned") if s == 0 else _('Partially signed') + ' (%d/%d)'%(s,r)