diff --git a/test/functional/feature_dersig.py b/test/functional/feature_dersig.py
--- a/test/functional/feature_dersig.py
+++ b/test/functional/feature_dersig.py
@@ -12,7 +12,6 @@
 from test_framework.mininode import *
 from test_framework.blocktools import create_coinbase, create_block
 from test_framework.script import CScript
-from io import BytesIO
 
 DERSIG_HEIGHT = 1251
 
@@ -46,9 +45,7 @@
     outputs = {to_address: amount}
     rawtx = node.createrawtransaction(inputs, outputs)
     signresult = node.signrawtransaction(rawtx)
-    tx = CTransaction()
-    tx.deserialize(BytesIO(hex_str_to_bytes(signresult['hex'])))
-    return tx
+    return FromHex(CTransaction(), signresult['hex'])
 
 
 class BIP66Test(BitcoinTestFramework):