diff --git a/lib/transaction.py b/lib/transaction.py
index 42b51f2f..fa4636f8 100644
--- a/lib/transaction.py
+++ b/lib/transaction.py
@@ -745,7 +745,7 @@ class Transaction:
                     for_sig = Hash(self.tx_for_sig(i).decode('hex'))
                     pkey = regenerate_key(sec)
                     secexp = pkey.secret
-                    private_key = ecdsa.SigningKey.from_secret_exponent( secexp, curve = SECP256k1 )
+                    private_key = bitcoin.MySigningKey.from_secret_exponent( secexp, curve = SECP256k1 )
                     public_key = private_key.get_verifying_key()
                     sig = private_key.sign_digest_deterministic( for_sig, hashfunc=hashlib.sha256, sigencode = ecdsa.util.sigencode_der )
                     assert public_key.verify_digest( sig, for_sig, sigdecode = ecdsa.util.sigdecode_der)