diff --git a/electrum/wallet.py b/electrum/wallet.py
index b9447e7c7..ed5906242 100644
--- a/electrum/wallet.py
+++ b/electrum/wallet.py
@@ -1440,6 +1440,7 @@ class Abstract_Wallet(AddressSynchronizer, ABC):
         if not isinstance(tx, PartialTransaction):
             tx = PartialTransaction.from_tx(tx)
         assert isinstance(tx, PartialTransaction)
+        tx.remove_signatures()
         if tx.is_final():
             raise CannotBumpFee(_('Transaction is final'))
         new_fee_rate = quantize_feerate(new_fee_rate)  # strip excess precision
diff --git a/electrum/wallet_db.py b/electrum/wallet_db.py
index 23d360915..281cd634a 100644
--- a/electrum/wallet_db.py
+++ b/electrum/wallet_db.py
@@ -968,6 +968,8 @@ class WalletDB(JsonDB):
         assert isinstance(tx_hash, str)
         assert isinstance(tx, Transaction), tx
         # note that tx might be a PartialTransaction
+        # serialize and de-serialize tx now. this might e.g. convert a complete PartialTx to a Tx
+        tx = tx_from_any(str(tx))
         if not tx_hash:
             raise Exception("trying to add tx to db without txid")
         if tx_hash != tx.txid():