diff --git a/bitcoinlib/wallets.py b/bitcoinlib/wallets.py
index 0451b271..2b134f92 100644
--- a/bitcoinlib/wallets.py
+++ b/bitcoinlib/wallets.py
@@ -4258,18 +4258,17 @@ def sweep(self, to_address, account_id=None, input_key_id=None, network=None, ma
             total_amount += utxo['value']
         srv = Service(network=network, wallet_name=self.name, providers=self.providers, cache_uri=self.db_cache_uri)
 
-        fee_modifier = 1 if self.witness_type == 'legacy' else 0.5
+        fee_modifier = 1 if self.witness_type == 'legacy' else 0.6
         if isinstance(fee, str):
-            n_outputs = 1 if not isinstance(to_address, list) else len(to_address)
             fee_per_kb = srv.estimatefee(priority=fee)
-            tr_size = 125 + (len(input_arr) * (77 + self.multisig_n_required * 72)) + n_outputs * 30
-            fee = int(100 + ((tr_size / 1000.0) * fee_per_kb * fee_modifier))
-
+            fee = None
         if not fee:
             if fee_per_kb is None:
                 fee_per_kb = srv.estimatefee()
-            tr_size = 125 + (len(input_arr) * 125)
-            fee = int((tr_size / 1000.0) * fee_per_kb * fee_modifier)
+            n_outputs = 1 if not isinstance(to_address, list) else len(to_address)
+            tr_size = 125 + (len(input_arr) * (77 + self.multisig_n_required * 72)) + n_outputs * 30
+            fee = int(100 + ((tr_size / 1000.0) * fee_per_kb * fee_modifier))
+
         if total_amount - fee <= self.network.dust_amount:
             raise WalletError("Amount to send is smaller then dust amount: %s" % (total_amount - fee))