diff --git a/test/functional/p2p_segwit.py b/test/functional/p2p_segwit.py
index 5c155384184..e99ecd80265 100755
--- a/test/functional/p2p_segwit.py
+++ b/test/functional/p2p_segwit.py
@@ -2097,14 +2097,14 @@ class SegWitTest(BitcoinTestFramework):
 
         raw = self.nodes[0].createrawtransaction([{"txid": unspent['txid'], "vout": unspent['vout']}], {self.nodes[0].getnewaddress(): 1})
         tx = FromHex(CTransaction(), raw)
-        assert_raises_rpc_error(-22, "TX decode failed", self.nodes[0].decoderawtransaction, serialize_with_bogus_witness(tx).hex())
+        assert_raises_rpc_error(-22, "TX decode failed", self.nodes[0].decoderawtransaction, hexstring=serialize_with_bogus_witness(tx).hex(), iswitness=True)
         with self.nodes[0].assert_debug_log(['Superfluous witness record']):
             self.test_node.send_and_ping(msg_bogus_tx(tx))
         raw = self.nodes[0].signrawtransactionwithwallet(raw)
         assert raw['complete']
         raw = raw['hex']
         tx = FromHex(CTransaction(), raw)
-        assert_raises_rpc_error(-22, "TX decode failed", self.nodes[0].decoderawtransaction, serialize_with_bogus_witness(tx).hex())
+        assert_raises_rpc_error(-22, "TX decode failed", self.nodes[0].decoderawtransaction, hexstring=serialize_with_bogus_witness(tx).hex(), iswitness=True)
         with self.nodes[0].assert_debug_log(['Unknown transaction optional data']):
             self.test_node.send_and_ping(msg_bogus_tx(tx))